<?php
# PHP MySQL to MySQLi migration shim library
# ------------------------------------------
# purpose: Redefines deprecated or missing mysql_ functions and calls
# mysqli_ functions for PHP 5.5+ and PHP 7+.
#
# author: Robert Klebe, dotpointer
#
# licensing: see LICENSE file
#
# notes
# -----
# mysql constants are directly translated to mysqli, so the actual value may
# 	differ
# mysql_escape_string now takes the last used connection

# to check if an item is a (mysql) resource or a mysqli object
# note that all types of resources must get through as this is a
# generic replacement for is_resource()
function is_mysqli_or_resource($r) {
  # get the type of the variable
  switch(gettype($r)) {
    # if it is a resource - could be mysql, file handle etc...
    case 'resource':
      return true;
    # if it is an object - must be a mysqli object then
    case 'object':
      # is this an instance of mysqli?
      if ($r instanceof mysqli) {
        # make sure there is no connection error
        return !($r->connect_error);
      }
      # or is this an instance of a mysqli result?
      if ($r instanceof mysqli_result) {
        return true;
      }
      return false;
    # negative on all other variable types
    default:
      return false;
  }
}

# alias for is_mysqli_or_resource()
function is_mysql_resource($r) {
  return is_mysqli_or_resource($r);
}

# alias for is_mysqli_or_resource()
function is_generic_resource($r) {
  return is_mysqli_or_resource($r);
}

# to check if an item is a resource/object - replace is_resource with this
# old version, this will break if testing file handles too
function is_mysql_resource_old($result) {

  # first try to treat as resource if original mysql is loaded
  if (extension_loaded('mysql')) {
    return is_resource($result);
  }

  # or if mysqli is loaded, try to check object
  if (extension_loaded('mysqli')) {
    return is_object($result);
  }

  echo 'Fatal error, mysqli extension not loaded.'."\n";
  die(1);
}

# only do this if mysql extension is not there
if (!extension_loaded('mysql')) {

  # check if mysqli extension is loaded - its required as we rely on it
  if (!extension_loaded('mysqli')) {
    echo 'Fatal error, mysqli extension not loaded.'."\n";
    die(1);
  }

# --- helper variables and constants -------------------------------------------

  # a list of connections, used to get the last one
  $mysql_links = array();

  # our own constants to reach default connection values in INI file
  if (!defined('MYSQL_DEFAULT_HOST')) {
    if (ini_get('mysqli.default_host') !== false) {
      define('MYSQL_DEFAULT_HOST', ini_get('mysqli.default_host'));
    } else {
      define('MYSQL_DEFAULT_HOST', ini_get('mysql.default_host'));
    }
  }

  if (!defined('MYSQL_DEFAULT_USER')) {
    if (ini_get('mysqli.default_user') !== false) {
      define('MYSQL_DEFAULT_USER', ini_get('mysqli.default_user'));
    } else {
      define('MYSQL_DEFAULT_USER', ini_get('mysql.default_user'));
    }
  }

  if (!defined('MYSQL_DEFAULT_PASSWORD')) {
    if (ini_get('mysqli.default_pw') !== false) {
      define('MYSQL_DEFAULT_PASSWORD', ini_get('mysqli.default_pw'));
    } else {
      define('MYSQL_DEFAULT_PASSWORD', ini_get('mysql.default_password'));
    }
  }

# --- MySQL constants (from PHP.net) -------------------------------------------

  # MySQL client constants

  # Use compression protocol
  define('MYSQL_CLIENT_COMPRESS', MYSQLI_CLIENT_COMPRESS);

  # Allow space after function names
  define('MYSQL_CLIENT_IGNORE_SPACE', MYSQLI_CLIENT_IGNORE_SPACE);

  # Allow interactive_timeout seconds
  # (instead of wait_timeout ) of
  # inactivity before closing the connection.
  define('MYSQL_CLIENT_INTERACTIVE', MYSQLI_CLIENT_INTERACTIVE);

  # Use SSL encryption. This flag is only
  # available with version 4.x of the MySQL
  # client library or newer. Version 3.23.x is
  # bundled both with PHP 4 and Windows binaries
  # of PHP 5.
  define('MYSQL_CLIENT_SSL', MYSQLI_CLIENT_SSL);

  # mysql_fetch_array() uses a constant for the different types of result
  # arrays. The following constants are defined:

  # MySQL fetch constants

  # Columns are returned into the array having
  # the fieldname as the array index.
  define('MYSQL_ASSOC', MYSQLI_ASSOC);

  # Columns are returned into the array having
  # both a numerical index and the fieldname as
  # the array index.
  define('MYSQL_BOTH', MYSQLI_BOTH);

  # Columns are returned into the array having a
  # numerical index to the fields. This index
  # starts with 0, the first field in the result.
  define('MYSQL_NUM', MYSQLI_NUM);

# --- helper functions ---------------------------------------------------------

  # internal function to convert bitflags of mysqli to flags in text
  # of mysql
  # thanks to andre at koethur dot de at
  # http://www.php.net/manual/en/mysqli-result.fetch-fields.php#101828
  function mysql_field_bitflags_to_flags($flags_num) {

    $flags = array();
    $constants = get_defined_constants(true);
    foreach ($constants['mysqli'] as $c => $n) {
      if (preg_match('/MYSQLI_(.*)_FLAG$/', $c, $m)) {
        if (!array_key_exists($n, $flags)) {
          $flags[$n] = $m[1];
        }
      }
    }
    $result = array();
    foreach ($flags as $n => $t) {
      if ($flags_num & $n) {
        $result[] = $t;
      }
    }
    return implode(' ', $result);
  }

  # function to convert bit-types of mysqli to types in text of mysql
  # thanks to andre at koethur dot de at
  # http://www.php.net/manual/en/mysqli-result.fetch-fields.php#101828
  function mysql_field_bittypes_to_types($type_id) {

    $types = array();
    $constants = get_defined_constants(true);
    foreach ($constants['mysqli'] as $c => $n) {
      if (preg_match('/^MYSQLI_TYPE_(.*)/', $c, $m)) {
        $types[$n] = $m[1];
      }
    }

    if (array_key_exists($type_id, $types)) {
      return $types[$type_id];
    }
    return NULL;
  }

  # lib helper function - to ensure mysql link as mysqli always needs
  # one but mysql takes last one
  function mysql_ensure_link($link_identifier) {
    # no link specified
    if ($link_identifier === NULL) {
      global $mysql_links;

      # no connection at all - then go null
      if (!count($mysql_links)) {
        return NULL;
      }

      # get the last item of the array
      $last = end($mysql_links);

      # return the last stored link
      return $last['link'];
    }

    return $link_identifier;
  }

# --- MySQL functions (from PHP.net) -------------------------------------------

  # mysql_affected_rows - Get number of affected rows in previous MySQL
  # operation
  # int mysql_affected_rows ([ resource $link_identifier = NULL ] )
  # int mysqli_affected_rows ( mysqli $link )
  function mysql_affected_rows($link_identifier = NULL) {
    # mysql_affected_rows = -1 if the last query failed
    # mysqli_affected_rows = -1 indicates that the query returned
    # an error
    # returns NULL on error natively, tested in PHP 5.6.3
    return mysqli_affected_rows(
      mysql_ensure_link($link_identifier)
    );
  }

  # mysql_client_encoding - Returns the name of the character set
  # string mysql_client_encoding ([ resource $link_identifier = NULL ] )
  # mysqli_character_set_name ( mysqli $link )
  function mysql_client_encoding($link_identifier = NULL) {
    # note that mysqlI_client_encoding ALSO is deprecated, so we
    # cannot it
    # mysql_client_encoding/mysqli_character_set_name = Returns
    # the default character set name for the current connection.
    # returns NULL on error natively, tested in PHP 5.6.3
    return mysqli_character_set_name(
      mysql_ensure_link($link_identifier)
    );
  }

  # mysql_close - Close MySQL connection
  # bool mysql_close ([ resource $link_identifier = NULL ] )
  # bool mysqli_close ( mysqli $link )
  function mysql_close($link = NULL) {

    # mysql_close/mysqli_close = returns TRUE on success or FALSE
    # on failure
    global $mysql_links;
    $link = mysql_ensure_link($link);

    if (isset($link->thread_id) && is_numeric($link->thread_id)) {
      $thread_id =  $link->thread_id;
    } else {
      $thread_id =  false;
    }

    $result = mysqli_close($link);

    # did the removal suceed and and we have thread id
    if ($result && $thread_id) {
      # walk the links
      foreach ($mysql_links as $k => $v) {

        # does this thread-id match the one we just
        # removed?
        if ($v['thread_id'] === $thread_id) {
          # then remove it from connection array
          array_splice($mysql_links, $k, 1);
          break;
        }
      }

    # when connection already has been closed this error appears:
    # Couldn't fetch mysqli in mysql-shim.php on line xxx
    # and this gives null instead of false
    } else if ($result === null) {
      return false;
    }

    return $result;
  }

  # mysql_connect - Open a connection to a MySQL Server
  # resource mysql_connect (
  # [ string $server = ini_get('mysql.default_host')
  # [, string $username = ini_get('mysql.default_user')
  # [, string $password = ini_get('mysql.default_password')
  # [, bool $new_link = false [, int $client_flags = 0 ]]]]] )
  # mysqli mysqli_connect (
  # [ string $host = ini_get('mysqli.default_host')
  # [, string $username = ini_get('mysqli.default_user')
  # [, string $passwd = ini_get('mysqli.default_pw')
  # [, string $dbname = ''
  # [, int $port = ini_get('mysqli.default_port')
  # [, string $socket = ini_get('mysqli.default_socket') ]]]]]] )
  function mysql_connect(
    $server = MYSQL_DEFAULT_HOST,
    $username = MYSQL_DEFAULT_USER,
    $password = MYSQL_DEFAULT_PASSWORD,
    $new_link = false, $client_flags = 0
  ) {
    global $mysql_links;

    # no new link but s/u/p matches previous ones-take last link
    if (!$new_link) {
      global $mysql_links;

      # are there previous links?
      if ($mysql_links && count($mysql_links)) {

        # get the last one made
        $last = end($mysql_links);

        # does the s/u/p match last one?
        if (
          $server === $last['server'] &&
          $username === $last['username'] &&
          $password === $last['password'] &&
          is_resource($last['link'])
        ) {
          # then take that
          return mysql_ensure_link(NULL);
        }
      }
    }

    # try to connect using current credentials
    $link = mysqli_connect($server, $username, $password, '');

    if (mysqli_connect_errno()) {
      # printf('Connect failed: %s'."\n",
      # mysqli_connect_error());
      # die();
      return false;
    }

    # store this
    $mysql_links[] = array(
      'thread_id' => $link->thread_id,
      'server' => $server,
      'username' => $username,
      'password' => $password,
      'link' => $link
    );

    return $link;
  }

  # mysql_createdb - Create a MySQL database - alias for mysql_create_db
  function mysql_createdb($database_name, $link_identifier = NULL) {
    # return mysql_create_db($database_name, $link_identifier);
    $link_identifier = mysql_ensure_link($link_identifier);
    return mysqli_query(
      $link_identifier,
      'CREATE DATABASE '.mysqli_real_escape_string(
        $link_identifier,
        $database_name
      )
    );
  }

  # mysql_create_db - Create a MySQL database
  # bool mysql_create_db ( string $database_name
  # [, resource $link_identifier = NULL ] )
  # CREATE DATABASE
  function mysql_create_db($database_name, $link_identifier = NULL) {
    # mysql_create_db/mysql_query+CREATE DATABASE = false on error
    # return mysql_query('CREATE DATABASE '.
    # mysql_real_escape_string($database_name), $link_identifier);
    $link_identifier = mysql_ensure_link($link_identifier);
    return mysqli_query(
      $link_identifier,
      'CREATE DATABASE '.mysqli_real_escape_string(
        $link_identifier,
        $database_name
      )
    );

  }

  # mysql_data_seek - Move internal result pointer
  # bool mysql_data_seek ( resource $result , int $row_number )
  # bool mysqli_data_seek ( mysqli_result $result , int $offset )
  function mysql_data_seek($result, $row_number) {
    # mysql_data_seek/mysqli_data_seek = false on error
    # returns NULL on error natively, tested in PHP 5.6.3
    return mysqli_data_seek($result, $row_number);
  }

  # mysql_db_name - Retrieves database name from the call to
  # mysql_list_dbs
  # string mysql_db_name ( resource $result , int $row
  # [, mixed $field = NULL ] )
  # SELECT DATABASE()
  function mysql_db_name($result, $row, $field = NULL) {
    # return mysql_query('SELECT DATABASE()',
    # mysql_ensure_link($link_identifier));
    # null does not fit mysql_result
    $field = $field === null ? 0 : $field;
    # return mysql_result($result, $row, $field);
    # below is from mysql_result
    if (mysqli_data_seek($result, $row) === false) {
      return false;
    }
    $row = mysqli_fetch_array($result);
    if ($row === NULL) {
      return $row;
    }
    if (!isset($row[$field])) {
      return false;
    }
    return $row[$field];
  }

  # mysql_dbname - Retrieves database name from the call to
  # mysql_list_dbs, alias for mysql_db_name
  function mysql_dbname($result, $row, $field = NULL) {
    # return mysql_db_name($result, $row, $field);
    if (mysqli_data_seek($result, $row) === false) {
      return false;
    }
    $row = mysqli_fetch_array($result);
    if ($row === NULL) {
      return $row;
    }
    if (!isset($row[$field])) {
      return false;
    }
    return $row[$field];
  }

  # mysql_db_query - Selects a database and executes a query on it
  # resource mysql_db_query ( string $database , string $query
  # [, resource $link_identifier = NULL ] )
  # mysqli_select_db() then the query
  function mysql_db_query($database, $query, $link_identifier = NULL) {
    # mysql_db_query = false on error, mysql_query+sql
    # = false on error
    # if (mysql_select_db($database, $link_identifier) !== true) {
    if (mysqli_select_db($link_identifier, $database) !== true) {
      return false;
    }
    # return mysql_query($query, $link_identifier);
    return mysqli_query($link_identifier, $query);
  }

  # mysql_drop_db - Drop (delete) a MySQL database
  # bool mysql_drop_db ( string $database_name
  # [, resource $link_identifier = NULL ] )
  # DROP DATABASE
  function mysql_drop_db($database_name, $link_identifier = NULL) {
    # mysql_drop_db = false on error, mysql_query + DROP DATABASE
    # = false on error
    # return mysql_query('DROP DATABASE '.
    # mysql_real_escape_string($database_name), $link_identifier);
    return mysqli_query(
      $link_identifier,
      'DROP DATABASE '.
      mysqli_real_escape_string(
        $link_identifier,
        $database_name
      )
    );
  }

  # mysql_errno -Returns the numerical value of the error message from
  # previous MySQL operation
  # int mysql_errno ([ resource $link_identifier = NULL ] )
  # int mysqli_errno ( mysqli $link )
  function mysql_errno($link_identifier = NULL) {
    # mysql_errno/mysqli_errno = returns a number, 0 if no error
    # returns NULL on error natively, tested in PHP 5.6.3
    return mysqli_errno (mysql_ensure_link($link_identifier));
  }

  # mysql_error - Returns the text of the error message from previous
  # MySQL operation
  # string mysql_error ([ resource $link_identifier = NULL ] )
  # string mysqli_error ( mysqli $link )
  function mysql_error($link_identifier = NULL) {
    # mysql_error/mysqli_error = returns empty string on no error
    # returns NULL on error natively, tested in PHP 5.6.3
    return mysqli_error(mysql_ensure_link($link_identifier));
  }

  # mysql_escape_string - Escapes a string for use in a # mysql_query
  # string mysql_escape_string ( string $unescaped_string )
  # string mysqli::real_escape_string ( string $escapestr )
  function mysql_escape_string($unescaped_string) {
    # mysql_escape_string = returns the escaped string
    # mysql_real_escape_string = returns FALSE on error
    # return mysql_real_escape_string($unescaped_string);
    return mysqli_real_escape_string(
      mysql_ensure_link(NULL),
      $unescaped_string
    );
  }

  # mysql_fetch_array - Fetch a result row as an associative array, a
  # numeric array, or both
  # array mysql_fetch_array ( resource $result
  # [, int $result_type = MYSQL_BOTH ] )
  # mixed mysqli_fetch_array ( mysqli_result $result
  # [, int $resulttype = MYSQLI_BOTH ] )
  function mysql_fetch_array($result, $result_type = MYSQL_BOTH) {
    # mysql_fetch_array = Returns an array of strings that
    # corresponds to the fetched row, or FALSE if there are no more
    # rows
    # mysqli_fetch_array = Returns an array of strings that
    # corresponds to the fetched row or NULL if there are no more
    # rows in resultset
    # returns NULL on error natively, tested in PHP 5.6.3
    return mysqli_fetch_array($result, $result_type);
  }

  # mysql_fetch_assoc - Fetch a result row as an associative array
  # array mysql_fetch_assoc ( resource $result )
  # array mysqli_fetch_assoc ( mysqli_result $result )
  function mysql_fetch_assoc($result) {
    # mysql_fetch_assoc = returns FALSE if there are no more rows
    # mysqli_fetch_assoc = returns NULL if there are no more rows in
    # resultset
    # returns NULL on error natively, tested in PHP 5.6.3
    return mysqli_fetch_assoc($result);
  }

  # mysql_fetch_field - Get column information from a result and
  # return as an object
  # object mysql_fetch_field ( resource $result
  # [, int $field_offset = 0 ] )
  # object mysqli_fetch_field ( mysqli_result $result ) - but
  # field_offset is missing
  function mysql_fetch_field($result, $field_offset = NULL) {
    # if field offset is specified
    if (is_numeric($field_offset)) {
      # then seek to that
      mysqli_field_seek($result, $field_offset);
    }
    # returns NULL on error natively, tested in PHP 5.6.3
    return mysqli_fetch_field($result);
  }

  # mysql_fetch_lengths - Get the length of each output in a result
  # array mysql_fetch_lengths ( resource $result )
  # array mysqli_fetch_lengths ( mysqli_result $result )
  function mysql_fetch_lengths($result) {
    # mysql_fetch_lengths/mysqli_fetch_lengths = FALSE on error
    # returns NULL on error natively, tested in PHP 5.6.3
    return mysqli_fetch_lengths($result);
  }

  # mysql_fetch_object - Fetch a result row as an object
  # object mysql_fetch_object ( resource $result [, string $class_name
  # [, array $params ]] )
  # object mysqli_fetch_object ( mysqli_result $result
  # [, string $class_name [, array $params ]] )
  function mysql_fetch_object($result, $class_name = NULL,
    $params = NULL
  ) {

    # mysql_fetch_object = FALSE if there are no more rows
    # mysqli_fetch_object = NULL if there are no more rows
    # in resultset

    if ($class_name !== NULL && $params !== NULL) {
      $t = mysqli_fetch_object($result, $class_name, $params);
    } else if ($class_name !== NULL) {
      $t = mysqli_fetch_object($result, $class_name);
    } else {
      $t = mysqli_fetch_object($result);
    }
    # is the result null?
    if ($t === NULL) {
      # then return false as the old function did
      return false;
    }
    return $t;
  }

  # mysql_fetch_row - Get a result row as an enumerated array
  # array mysql_fetch_row ( resource $result )
  # mixed mysqli_fetch_row ( mysqli_result $result )
  function mysql_fetch_row($result) {

    # mysql_fetch_row = FALSE if there are no more rows
    # mysqli_fetch_row = NULL if there are no more rows in
    # result set
    # returns NULL on error natively, tested in PHP 5.6.3
    return mysqli_fetch_row($result);
  }

  # mysql_field_flags - Get the flags associated with the specified
  # field in a result
  # string mysql_field_flags ( resource $result , int $field_offset )
  # mysqli_fetch_field_direct() [flags]
  # -> object mysqli_fetch_field_direct ( mysqli_result $result ,
  # int $fieldnr )
  function mysql_field_flags($result, $field_offset) {
    # mysql_field_flags = FALSE on failure
    # mysqli_fetch_field_direct = FALSE if no field information for
    # specified fieldnr is available
    # returns NULL on error natively, tested in PHP 5.6.3
    $t = mysqli_fetch_field_direct($result, $field_offset);
    if (!is_object($t)) return $t;
    $t = (array)$t;
    if (isset($t['flags'])) {
      return mysql_field_bitflags_to_flags($t['flags']);
    }
    return NULL;
  }

  # mysql_field_len - Returns the length of the specified field
  # int mysql_field_len ( resource $result , int $field_offset )
  # mysqli_fetch_field_direct() [length]
  # -> object mysqli_fetch_field_direct ( mysqli_result $result ,
  # int $fieldnr )
  function mysql_field_len($result, $field_offset) {
    # mysql_field_len = FALSE on failure
    # mysqli_fetch_field_direct = FALSE if no field information for
    # specified fieldnr is available
    # returns NULL on error natively, tested in PHP 5.6.3
    $t = mysqli_fetch_field_direct($result, $field_offset);
    if (!is_object($t)) return $t;
    $t = (array)$t;
    return isset($t['length']) ? $t['length'] : NULL;
  }

  # mysql_field_name - Get the name of the specified field in a result
  # string mysql_field_name ( resource $result , int $field_offset )
  # mysqli_fetch_field_direct() [name] or [orgname]
  # -> object mysqli_fetch_field_direct ( mysqli_result $result ,
  # int $fieldnr )
  function mysql_field_name($result, $field_offset) {
    # mysql_field_name = FALSE on failure
    # mysqli_fetch_field_direct = FALSE if no field information for
    # specified fieldnr is available
    # returns NULL on error natively, tested in PHP 5.6.3
    $t = mysqli_fetch_field_direct($result, $field_offset);
    if (!is_object($t)) return $t;
    $t = (array)$t;
    return isset($t['name']) ? $t['name'] : NULL;
  }

  # mysql_field_seek - Set result pointer to a specified field offset
  # bool mysql_field_seek ( resource $result , int $field_offset )
  # bool mysqli_field_seek ( mysqli_result $result , int $fieldnr )
  function mysql_field_seek($result, $field_offset) {
    # mysql_field_seek/mysqli_field_seek = FALSE on failure
    # returns NULL on error natively, tested in PHP 5.6.3
    return mysqli_field_seek($result, $field_offset);
  }

  # mysql_field_table - Get name of the table the specified field is in
  # string mysql_field_table ( resource $result , int $field_offset )
  # mysqli_fetch_field_direct() [table] or [orgtable]
  # -> object mysqli_fetch_field_direct ( mysqli_result $result ,
  # int $fieldnr )
  function mysql_field_table($result, $field_offset) {
    # mysql_field_table = error return value not defined
    # mysqli_fetch_field_direct = FALSE if no field information for
    # specified fieldnr is available
    # returns NULL on error natively, tested in PHP 5.6.3
    $t = mysqli_fetch_field_direct($result, $field_offset);
    if (!is_object($t)) return $t;
    $t = (array)$t;
    return isset($t['table']) ? $t['table'] : NULL;
  }

  # mysql_field_type - Get the type of the specified field in a result
  # string mysql_field_type ( resource $result , int $field_offset )
  # mysqli_fetch_field_direct() [type]
  # -> object mysqli_fetch_field_direct ( mysqli_result $result ,
  # int $fieldnr )
  function mysql_field_type($result, $field_offset) {
    # mysql_field_type = error return value not defined
    # mysqli_fetch_field_direct = FALSE if no field information for
    # specified fieldnr is available
    # returns NULL on error natively, tested in PHP 5.6.3
    $t = mysqli_fetch_field_direct($result, $field_offset);
    if (!is_object($t)) return $t;
    $t = (array)$t;
    if (isset($t['type'])) {
      return mysql_field_bittypes_to_types($t['type']);
    }
    return NULL;
  }

  # mysql_free_result - Free result memory
  # bool mysql_free_result ( resource $result )
  # void mysqli_free_result ( mysqli_result $result )
  function mysql_free_result($result) {
    # mysql_free_result = FALSE on failure
    # mysqli_free_result = No value is returned.
    mysqli_free_result($result);
    # note that mysqli does not return any boolean, so we do it
    return true;
  }

  # mysql_get_client_info - Get MySQL client info
  # string mysql_get_client_info ( void )
  # string mysqli_get_client_info ( mysqli $link )
  function mysql_get_client_info($link_identifier = null) {
    # mysql_get_client_info/mysqli_get_client_info = not defined
    # what is returned on error
    # note that mysql does not have a link argument while mysqli does
    return mysqli_get_client_info(
      mysql_ensure_link($link_identifier)
    );
  }

  # mysql_get_host_info - Get MySQL host info
  # string mysql_get_host_info ([ resource $link_identifier = NULL ] )
  # string mysqli_get_host_info ( mysqli $link )
  function mysql_get_host_info($link_identifier = NULL) {
    # mysql_get_host_info = FALSE on failure
    # mysqli_get_host_info = error return value not defined
    # returns NULL on error natively, tested in PHP 5.6.3
    return mysqli_get_host_info(
      mysql_ensure_link($link_identifier)
    );
  }

  # mysql_get_proto_info - Get MySQL protocol info
  # int mysql_get_proto_info ([ resource $link_identifier = NULL ] )
  # int mysqli_get_proto_info ( mysqli $link )
  function mysql_get_proto_info($link_identifier = NULL) {
    # mysql_get_proto_info = FALSE on failure
    # mysqli_get_proto_info = error return value not defined
    # returns NULL on error natively, tested in PHP 5.6.3
    return mysqli_get_proto_info(
      mysql_ensure_link($link_identifier)
    );
  }

  # mysql_get_server_info - Get MySQL server info
  # string mysql_get_server_info ([ resource $link_identifier = NULL ] )
  # string mysqli_get_server_info ( mysqli $link )
  function mysql_get_server_info($link_identifier = NULL) {
    # mysql_get_server_info = FALSE on failure
    # mysqli_get_server_info = error return value not defined
    # returns NULL on error natively, tested in PHP 5.6.3
    return mysqli_get_server_info(
      mysql_ensure_link($link_identifier)
    );
  }

  # mysql_info - Get information about the most recent query
  # string mysql_info ([ resource $link_identifier = NULL ] )
  # string mysqli_info ( mysqli $link )
  function mysql_info($link_identifier = NULL) {
    # mysql_info = FALSE on failure
    # mysqli_info = returns empty string on failure
    # returns NULL on error natively, tested in PHP 5.6.3
    return mysqli_info(
      mysql_ensure_link($link_identifier)
    );
  }

  # mysql_insert_id - Get the ID generated in the last query
  # int mysql_insert_id ([ resource $link_identifier = NULL ] )
  # mixed mysqli_insert_id ( mysqli $link )
  function mysql_insert_id($link_identifier = NULL) {
    # mysql_insert_id = FALSE if no MySQL connection was
    # established
    # mysqli_insert_id = error value not defined
    # returns NULL on error natively, tested in PHP 5.6.3
    return mysqli_insert_id(
      mysql_ensure_link($link_identifier)
    );
  }

  # mysql_list_dbs - List databases available on a MySQL server
  # resource mysql_list_dbs ([ resource $link_identifier = NULL ] )
  # SQL Query: SHOW DATABASES
  function mysql_list_dbs($link_identifier = NULL) {
    global $mysql_list_dbs_cache;

    # mysql_list_dbs/mysql_query = FALSE on failure
    # $t = mysql_query('SHOW DATABASES',
    # mysql_ensure_link($link_identifier));
    $t = mysqli_query(
      mysql_ensure_link($link_identifier),
      'SHOW DATABASES'
    );

    $mysql_list_dbs_cache = $t;
    # when no working link is passed we get null
    # returns NULL on error natively, tested in PHP 5.6.3
    return $t;
  }

  # mysql_list_fields - List MySQL table fields
  # resource mysql_list_fields ( string $database_name ,
  # string $table_name [, resource $link_identifier = NULL ] )
  # SQL Query: SHOW COLUMNS FROM sometable
  function mysql_list_fields($database_name, $table_name,
    $link_identifier = NULL
  ) {
    # mysql_list_fields/mysql_query = FALSE on failure
    $link_identifier = mysql_ensure_link($link_identifier);
    # return mysql_query('SHOW COLUMNS FROM '.
    # mysql_real_escape_string($database_name).'.`'.
    # mysql_real_escape_string($table_name).'`',
    # mysql_ensure_link($link_identifier));
    return mysqli_query(
      $link_identifier,
      'SHOW COLUMNS FROM '.
      mysqli_real_escape_string($link_identifier, $database_name).
      '.`'.
      mysqli_real_escape_string($link_identifier, $table_name).
      '`'
    );
  }

  # mysql_list_processes - List MySQL processes
  # resource mysql_list_processes
  # ([ resource $link_identifier = NULL ] )
  # mysqli_thread_id()
  function mysql_list_processes($link_identifier = NULL) {
    # mysql_list_processes = FALSE on failure
    # returns NULL on error natively, tested in PHP 5.6.3
    # return mysql_query('SHOW PROCESSLIST',
    # mysql_ensure_link($link_identifier));
    return mysqli_query(
      mysql_ensure_link($link_identifier),
      'SHOW PROCESSLIST'
    );
  }

  # mysql_list_tables - List tables in a MySQL database
  # resource mysql_list_tables ( string $database
  # [, resource $link_identifier = NULL ] )
  # SQL Query: SHOW TABLES FROM sometable
  function mysql_list_tables($database_name, $table_name,
    $link_identifier = NULL
  ) {
    # mysql_list_tables/mysql_query = FALSE on failure
    $link_identifier = mysql_ensure_link($link_identifier);
    # return mysql_query('SHOW TABLES FROM '.
    # mysql_real_escape_string($database_name),
    # mysql_ensure_link($link_identifier));
    return mysqli_query(
      $link_identifier,
      'SHOW TABLES FROM '.
      mysqli_real_escape_string($link_identifier, $database_name)
    );
  }

  # mysql_num_fields - Get number of fields in result
  # int mysql_num_fields ( resource $result )
  # int mysqli_field_count ( mysqli $link )
  function mysql_num_fields($result) {

    # mysql_num_fields/mysqli_fetch_fields = FALSE on failure

    # mysql takes a result, where mysqli takes link and takes the most
    # recent query
    # so instead we fetch all the fields and then count that
    $t = mysqli_fetch_fields($result);
    # returns NULL on error natively, tested in PHP 5.6.3
    if ($t === null) {
      return $t;
    }
    return count($t);
  }

  # mysql_num_rows - Get number of rows in result
  # int mysql_num_rows ( resource $result )
  # int mysqli_num_rows ( mysqli_result $result )
  function mysql_num_rows($result) {
    # mysql_num_rows = FALSE on failure
    # mysqli_num_rows = NULL on failure
    # returns NULL on error natively, tested in PHP 5.6.3
    return mysqli_num_rows($result);
  }

  # mysql_pconnect - Open a persistent connection to a MySQL server
  # resource mysql_pconnect ([ string $server =
  # ini_get("mysql.default_host")
  # [, string $username = ini_get("mysql.default_user")
  # [, string $password = ini_get("mysql.default_password")
  # [, int $client_flags = 0 ]]]] )
  # mysqli_connect() with p: host prefix
  function mysql_pconnect($server = MYSQL_DEFAULT_HOST,
    $username = MYSQL_DEFAULT_USER,
    $password = MYSQL_DEFAULT_PASSWORD,
    $client_flags = 0
  ) {
    # mysql_pconnect/mysql_connect = FALSE on error
    return mysql_connect(
      'p:'.$server,
      $username,
      $password,
      true,
      $client_flags
    );
  }

  # mysql_ping - Ping a server connection or reconnect if there is no
  # connection
  # bool mysql_ping ([ resource $link_identifier = NULL ] )
  # bool mysqli_ping ( mysqli $link )
  function mysql_ping($link_identifier = NULL) {
    # mysql_ping/mysqli_ping = FALSE on error
    return mysqli_ping(mysql_ensure_link($link_identifier));
  }

  # mysql_query - Send a MySQL query
  # resource mysql_query ( string $query
  # [, resource $link_identifier = NULL ] )
  # mixed mysqli_query ( mysqli $link , string $query
  # [, int $resultmode = MYSQLI_STORE_RESULT ] )
  function mysql_query($query, $link_identifier = NULL) {
    # mysql_query/mysqli_query = FALSE on error
    return mysqli_query(mysql_ensure_link($link_identifier), $query);
  }

  # mysql_real_escape_string - Escapes special characters in a
  # string for use in an SQL statement
  # string mysql_real_escape_string ( string $unescaped_string
  # [, resource $link_identifier = NULL ] )
  # string mysqli_real_escape_string ( mysqli $link ,
  # string $escapestr )
  function mysql_real_escape_string($unescaped_string,
    $link_identifier = NULL
  ) {
    # mysql_real_escape_string = FALSE on error
    # mysqli_real_escape_string = error return value not defined
    # returns NULL on error natively, tested in PHP 5.6.3
    return mysqli_real_escape_string(
      mysql_ensure_link($link_identifier),
      $unescaped_string
    );
  }

  # mysql_result - Get result data
  # string mysql_result ( resource $result , int $row [,
  # mixed $field = 0 ] )
  # no equivalent function exists in mysqli - mysqli_data_seek() in
  # conjunction with mysqli_field_seek() and mysqli_fetch_field()
  function mysql_result($result, $row, $field = 0) {
    # mysql_result = FALSE on failure
    # try to seek position, returns false on failure
    # returns NULL on error natively, tested in PHP 5.6.3
    if (mysqli_data_seek($result, $row) === false) return false;
    $row = mysqli_fetch_array($result);
    if ($row === NULL) return $row;
    if (!array_key_exists($field, $row)) {
      $row = array_change_key_case($row, CASE_LOWER);
      $field = strtolower($field);
      if (!array_key_exists($field, $row)) {
        return false;
      }
    }
    return $row[$field];
  }

  # mysql_select_db - Select a MySQL database
  # bool mysql_select_db ( string $database_name
  # [, resource $link_identifier = NULL ] )
  function mysql_select_db($database_name, $link_identifier = NULL) {
    # mysql_select_db/mysqli_select_db = FALSE on failure
    return mysqli_select_db(
      mysql_ensure_link($link_identifier),
      $database_name
    );
  }

  # alias for mysql_select_db
  function mysql_selectdb($database_name, $link_identifier = NULL) {
    return mysql_select_db ($database_name, $link_identifier = NULL);
  }

  # mysql_set_charset - Sets the client character set
  # bool mysql_set_charset ( string $charset
  # [, resource $link_identifier = NULL ] )
  # bool mysqli_set_charset ( mysqli $link , string $charset )
  function mysql_set_charset($charset, $link_identifier = NULL) {
    # mysql_set_charset/mysqli_set_charset = FALSE on failure
    return mysqli_set_charset(
      mysql_ensure_link($link_identifier),
      $charset
    );
  }

  # mysql_stat - Get current system status
  # string mysql_stat ([ resource $link_identifier = NULL ] )
  # string mysqli_stat ( mysqli $link )
  function mysql_stat($link_identifier = NULL) {
    # mysql_stat = NULL on error
    # mysqli_stat = FALSE on error
    $t = mysqli_stat(mysql_ensure_link($link_identifier));
    if ($t === FALSE) {
      return NULL;
    }
    return $t;
  }

  # mysql_tablename - Get table name of field
  # string mysql_tablename ( resource $result , int $i )
  # no mysqli equivalent exists -
  # SHOW TABLES [FROM db_name] [LIKE 'pattern']
  function mysql_tablename($result, $i) {
    # return mysql_query('SHOW COLUMNS FROM "'.
    # mysql_real_escape_string($database_name).'.'.
    # mysql_real_escape_string($table_name).'"',
    # mysql_ensure_link($link_identifier));
    # return mysql_result($result, $i);

    # below based on mysql_result
    $row = $i;
    $field = 0;
    # mysql_result = FALSE on failure
    # try to seek position, returns false on failure
    # returns NULL on error natively, tested in PHP 5.6.3
    if (mysqli_data_seek($result, $row) === false) {
      return false;
    }
    $row = mysqli_fetch_array($result);
    if ($row === NULL) {
      return $row;
    }
    if (!isset($row[$field])) {
      return false;
    }
    return $row[$field];
  }

  # mysql_thread_id - Return the current thread ID
  # int mysql_thread_id ([ resource $link_identifier = NULL ] )
  # int mysqli_thread_id ( mysqli $link )
  function mysql_thread_id($link_identifier = NULL) {
    # mysql_thread_id = FALSE on failure
    # mysqli_thread_id = no error return value defined
    # returns NULL on error natively, tested in PHP 5.6.3
    return mysqli_thread_id(mysql_ensure_link($link_identifier));
  }

  # mysql_unbuffered_query - Send an SQL query to MySQL without
  # fetching and buffering the result rows
  # resource mysql_unbuffered_query ( string $query
  # [, resource $link_identifier = NULL ] )
  # no mysqli equivalent exists - use mysqli_query with
  # MYSQLI_USE_RESULT parameter
  function mysql_unbuffered_query($query, $link_identifier = NULL) {
    # mysql_unbuffered_query/mysqli_query = FALSE on error
    return mysqli_query(
      mysql_ensure_link($link_identifier),
      $query,
      MYSQLI_USE_RESULT
    );
  }
}