Copyright 1997-2012 the PHP Documentation Group.

The plugin is implemented as a PHP extension. See the installation instructions to install the PECL/mysqlnd_uh extension. Then, load the extension into PHP and activate the plugin in the PHP configuration file using the PHP configuration directive named mysqlnd_uh.enable. The below example shows the default settings of the extension.

mysqlnd_uh.enable=1
mysqlnd_uh.report_wrong_types=1

Copyright 1997-2012 the PHP Documentation Group.

This describes the background and inner workings of the mysqlnd_uh extension.

Two classes are provided by the extension: MysqlndUhConnection and MysqlndUhPreparedStatement. MysqlndUhConnection lets you access almost all methods of the mysqlnd internal connection class. The latter exposes some selected methods of the mysqlnd internal statement class. For example, MysqlndUhConnection::connect maps to the mysqlnd library C function mysqlnd_conn__connect.

As a mysqlnd plugin, the PECL/mysqlnd_uh extension replaces mysqlnd library C functions with its own functions. Whenever a PHP MySQL extension compiled to use mysqlnd calls a mysqlnd function, the functions installed by the plugin are executed instead of the original mysqlnd ones. For example, mysqli_connect invokes mysqlnd_conn__connect, so the connect function installed by PECL/mysqlnd_uh will be called. The functions installed by PECL/mysqlnd_uh are the methods of the built-in classes.

The built-in PHP classes and their methods do nothing but call their mysqlnd C library counterparts, to behave exactly like the original mysqlnd function they replace. The code below illustrates in pseudo-code what the extension does.

class MysqlndUhConnection {
  public function connect(($conn, $host, $user, $passwd, $db, $port, $socket, $mysql_flags) {
    MYSQLND* c_mysqlnd_connection = convert_from_php_to_c($conn);
    ...
    return call_c_function(mysqlnd_conn__connect(c_mysqlnd_connection, ...));
  }
}

The build-in classes behave like a transparent proxy. It is possible for you to replace the proxy with your own. This is done by subclassing MysqlndUhConnection or MysqlndUhPreparedStatement to extend the functionality of the proxy, followed by registering a new proxy object. Proxy objects are installed by mysqlnd_uh_set_connection_proxy and mysqlnd_uh_set_statement_proxy.

<?php
class proxy extends MysqlndUhConnection {
 public function connect($res, $host, $user, $passwd, $db, $port, $socket, $mysql_flags) {
   printf("%s(%s)\n", __METHOD__, var_export(func_get_args(), true));
   $ret = parent::connect($res, $host, $user, $passwd, $db, $port, $socket, $mysql_flags);
   printf("%s returns %s\n", __METHOD__, var_export($ret, true));
   return $ret;
 }
}
mysqlnd_uh_set_connection_proxy(new proxy());

$mysqli = new mysqli("localhost", "root", "", "test");
?>

    

proxy::connect(array (
  0 => NULL,
  1 => 'localhost',
  2 => 'root',
  3 => '',
  4 => 'test',
  5 => 3306,
  6 => NULL,
  7 => 131072,
))
proxy::connect returns true

Copyright 1997-2012 the PHP Documentation Group.

The extension provides two built-in classes: MysqlndUhConnection and MysqlndUhPreparedStatement. The classes are used for hooking mysqlnd library calls. Their methods correspond to mysqlnd internal functions. By default they act like a transparent proxy and do nothing but call their mysqlnd counterparts. By subclassing the classes you can install your own proxy to monitor mysqlnd.

See also the How it works guide to learn about the inner workings of this extension.

Connection proxies are objects of the type MysqlndUhConnection. Connection proxy objects are installed by mysqlnd_uh_set_connection_proxy. If you install the built-in class MysqlndUhConnection as a proxy, nothing happens. It behaves like a transparent proxy.

<?php
mysqlnd_uh_set_connection_proxy(new MysqlndUhConnection());
$mysqli = new mysqli("localhost", "root", "", "test");
?>

The PHP_INI_SYSTEM configuration setting mysqlnd_uh.enable controls whether a proxy may be set. If disabled, the extension will throw errors of type E_WARNING

mysqlnd_uh.enable=0

    

<?php
mysqlnd_uh_set_connection_proxy(new MysqlndUhConnection());
$mysqli = new mysqli("localhost", "root", "", "test");
?>

    

PHP Warning:  MysqlndUhConnection::__construct(): (Mysqlnd User Handler) The plugin has been disabled by setting the configuration parameter mysqlnd_uh.enabled = false.  You must not use any of the base classes in %s on line %d
PHP Warning:  mysqlnd_uh_set_connection_proxy(): (Mysqlnd User Handler) The plugin has been disabled by setting the configuration parameter mysqlnd_uh.enable = false. The proxy has not been installed  in %s on line %d

To monitor mysqlnd, you have to write your own proxy object subclassing MysqlndUhConnection. Please, see the function reference for a the list of methods that can be subclassed. Alternatively, you can use reflection to inspect the built-in MysqlndUhConnection.

Create a new class proxy. Derive it from the built-in class MysqlndUhConnection. Replace the MysqlndUhConnection::connect. method. Print out the host parameter value passed to the method. Make sure that you call the parent implementation of the connect method. Failing to do so may give unexpected and undesired results, including memory leaks and crashes.

Register your proxy and open three connections using the PHP MySQL extensions mysqli, mysql, PDO_MYSQL. If the extensions have been compiled to use the mysqlnd library, the proxy::connect method will be called three times, once for each connection opened.

<?php
class proxy extends MysqlndUhConnection {
  public function connect($res, $host, $user, $passwd, $db, $port, $socket, $mysql_flags) {
   printf("Connection opened to '%s'\n", $host);
   /* Always call the parent implementation! */
   return parent::connect($res, $host, $user, $passwd, $db, $port, $socket, $mysql_flags);
  }
}
mysqlnd_uh_set_connection_proxy(new proxy());

$mysqli = new mysqli("localhost", "root", "", "test");
$mysql = mysql_connect("localhost", "root", "");
$pdo = new PDO("mysql:host=localhost;dbname=test", "root", "");
?>

    

Connection opened to 'localhost'
Connection opened to 'localhost'
Connection opened to 'localhost'

The use of prepared statement proxies follows the same pattern: create a proxy object of the type MysqlndUhPreparedStatement and install the proxy using mysqlnd_uh_set_statement_proxy.

<?php
class stmt_proxy extends MysqlndUhPreparedStatement {
 public function prepare($res, $query) {
  printf("%s(%s)\n", __METHOD__, $query);
  return parent::prepare($res, $query);
 }
}
mysqlnd_uh_set_statement_proxy(new stmt_proxy());

$mysqli = new mysqli("localhost", "root", "", "test");
$stmt = $mysqli->prepare("SELECT 'mysqlnd hacking made easy' AS _msg FROM DUAL");
?>

    

stmt_proxy::prepare(SELECT 'mysqlnd hacking made easy' AS _msg FROM DUAL)

Copyright 1997-2012 the PHP Documentation Group.

Basic monitoring of a query statement is easy with PECL/mysqlnd_uh. Combined with debug_print_backtrace it can become a powerful tool, for example, to find the origin of certain statement. This may be desired when searching for slow queries but also after database refactoring to find code still accessing deprecated databases or tables. The latter may be a complicated matter to do otherwise, especially if the application uses auto-generated queries.

<?php
class conn_proxy extends MysqlndUhConnection {
 public function query($res, $query) {
  debug_print_backtrace();
  return parent::query($res, $query);
 }
}
class stmt_proxy extends MysqlndUhPreparedStatement {
 public function prepare($res, $query) {
  debug_print_backtrace();
  return parent::prepare($res, $query);
 }
}
mysqlnd_uh_set_connection_proxy(new conn_proxy());
mysqlnd_uh_set_statement_proxy(new stmt_proxy());

printf("Proxies installed...\n");
$pdo = new PDO("mysql:host=localhost;dbname=test", "root", "");
var_dump($pdo->query("SELECT 1 AS _one FROM DUAL")->fetchAll(PDO::FETCH_ASSOC));

$mysqli = new mysqli("localhost", "root", "", "test");
$mysqli->prepare("SELECT 1 AS _two FROM DUAL");
?>

    

#0  conn_proxy->query(Resource id #19, SELECT 1 AS _one FROM DUAL)
#1  PDO->query(SELECT 1 AS _one FROM DUAL) called at [example.php:19]
array(1) {
  [0]=>
  array(1) {
    ["_one"]=>
    string(1) "1"
  }
}
#0  stmt_proxy->prepare(Resource id #753, SELECT 1 AS _two FROM DUAL)
#1  mysqli->prepare(SELECT 1 AS _two FROM DUAL) called at [example.php:22]

For basic query monitoring you should install a connection and a prepared statement proxy. The connection proxy should subclass MysqlndUhConnection::query. All database queries not using native prepared statements will call this method. In the example the query function is invoked by a PDO call. By default, PDO_MySQL is using prepared statement emulation.

All native prepared statements are prepared with the prepare method of mysqlnd exported through MysqlndUhPreparedStatement::prepare. Subclass MysqlndUhPreparedStatement and overwrite prepare for native prepared statement monitoring.