php-doc-en/reference/mysqli/mysqlnd.xml

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<chapter xml:id="mysqli.mysqlnd" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">

 <title>The MySQL Native Driver</title>

 <para>
  This section of the manual provides an overview of the MySQL Native
  Driver.
 </para>

 <para>
  <emphasis role="bold">What is it?</emphasis>
 </para>

 <para>
  MySQL Native Driver is a replacement for the MySQL Client Library
  (libmysql). MySQL Native Driver is part of the official PHP 5.3 and
  PHP 6 branches.
 </para>

 <para>
  The MySQL database extensions MySQL extension,
  <literal>mysqli</literal> and PDO MYSQL all communicate with the MySQL
  server. In the past, this was done by the extension using the services
  provided by the MySQL Client Library. The extensions were compiled
  against the MySQL Client Library in order to use its client-server
  protocol.
 </para>

 <para>
  With MySQL Native Driver there is now an alternative, as the MySQL
  database extensions can be compiled to use MySQL Native Driver instead
  of the MySQL Client Library.
 </para>

 <para>
  MySQL Native Driver is written in C as a PHP extension.
 </para>

 <para>
  <emphasis role="bold">What it is not</emphasis>
 </para>

 <para>
  Although MySQL Native Driver is written as a PHP extension, it is
  important to note that it does not provide a new API to the PHP
  programmer. The programmer APIs for MySQL database connectivity are
  provided by the MySQL extension, <literal>mysqli</literal> and PDO
  MYSQL. These extensions can now use the services of MySQL Native
  Driver to communicate with the MySQL Server. Therefore, you should not
  think of MySQL Native Driver as an API.
 </para>

 <para>
  <emphasis role="bold">Why use it?</emphasis>
 </para>

 <para>
  Using the MySQL Native Driver offers a number of advantages over using
  the MySQL Client Library.
 </para>

 <para>
  The older MySQL Client Library was written by MySQL AB and so was
  released under the MySQL license. This ultimately led to MySQL support
  being disabled by default in PHP. However, the MySQL Native Driver has
  been developed as part of the PHP project, and is therefore released
  under the PHP license. This removes licensing issues that have been
  problematic in the past.
 </para>

 <para>
  Also, in the past, you needed to build the MySQL database extensions
  against a copy of the MySQL Client Library. This typically meant you
  needed to have MySQL installed on a machine where you were building
  the PHP source code. Also, when your PHP application was running, the
  MySQL database extensions would call down to the MySQL Client library
  file at run time, so the file needed to be installed on your system.
  With MySQL Native Driver that is no longer the case as it is included
  as part of the standard distribution. So you do not need MySQL
  installed in order to build PHP or run PHP database applications.
 </para>

 <para>
  Because MySQL Native Driver is written as a PHP extension, it is
  tightly coupled to the workings of PHP. This leads to gains in
  efficiency, especially when it comes to memory usage, as the driver
  uses the PHP memory management system. It also supports the PHP memory
  limit. Using MySQL Native Driver leads to comparable or better
  performance than using MySQL Client Library, it always ensures the
  most efficient use of memory. One example of the memory efficiency is
  the fact that when using the MySQL Client Library, each row is stored
  in memory twice, whereas with the MySQL Native Driver each row is only
  stored once in memory.
 </para>

 <para>
  <emphasis role="bold">Special features</emphasis>
 </para>

 <para>
  MySQL Native Driver also provides some special features not available
  when the MySQL database extensions use MySQL Client Library. These
  special features are listed below:
 </para>

 <itemizedlist>

  <listitem>
   <para>
    Improved persistent connections
   </para>
  </listitem>

  <listitem>
   <para>
    The special function <function>mysqli_fetch_all</function>
   </para>
  </listitem>

  <listitem>
   <para>
    Performance statistics calls:
    <function>mysqli_get_cache_stats</function>,
    <function>mysqli_get_client_stats</function>,
    <function>mysqli_get_connection_stats</function>
   </para>
  </listitem>

 </itemizedlist>

 <para>
  The performance statistics facility can prove to be very useful in
  identifying performance bottlenecks.
 </para>

 <para>
  MySQL Native Driver also allows for persistent connections when used
  with the <literal>mysqli</literal> extension.
 </para>

 <para>
  <emphasis role="bold">Installation on Unix</emphasis>
 </para>

 <para>
  By default the MySQL database extensions are configured to use MySQL
  Client Library. In order to use the MySQL Native Driver, PHP needs to
  be built specifying that the MySQL database extensions are compiled
  with MySQL Native Driver support. This is done through configuration
  options prior to building the PHP source code.
 </para>

 <para>
  For example, to build the MySQL extension, <literal>mysqli</literal>
  and PDO MYSQL using the MySQL Native Driver, the following command
  would be given:
 </para>

<programlisting role="shell">./configure --with-mysql=mysqlnd \
--with-mysqli=mysqlnd \
--with-pdo-mysql=mysqlnd \
[other options]</programlisting>

 <para>
  <emphasis role="bold">Installation on Windows</emphasis>
 </para>

 <para>
  In the official PHP distributions from 5.3 onwards, MySQL Native
  Driver is enabled by default, so no additional configuration is
  required to use it. All MySQL database extensions will use MySQL
  Native Driver in this case.
 </para>

 <para>
  <emphasis role="bold">Using Persistent Connections</emphasis>
 </para>

 <para>
  The MySQL database extensions do not support persistent connections
  when used with the MySQL Client Library. However, they do when using
  MySQL Native Driver. When creating a connection the hostname is
  prepended with <quote>p:</quote>. This is demonstrated by the
  following code snippet, which creates a new connection using
  <literal>mysqli</literal>:
 </para>

<programlisting role="php">$host="p:localhost";
$port=3306;
$socket="/tmp/mysql.sock";
$user="root";
$password="password";
$dbname="test";

$conn = new mysqli($host, $user, $password, $dbname, $port, $socket)
   or die ('Could not connect to the database server' . mysqli_connect_error());</programlisting>

 <para>
  <emphasis role="bold">Using
  <function>mysqli_fetch_all</function></emphasis>
 </para>

 <para>
  If you are using <literal>mysqli</literal> with the MySQL Native
  Driver, you have access to the new API call
  <function>mysqli_fetch_all</function>.
 </para>

 <para>
  As <function>mysqli_fetch_all</function> returns all the rows as an
  array in a single step, it may consume more memory than some similar
  functions such as <function>mysqli_fetch_array</function>, which only
  returns one row at a time from the result set. Further, if you need to
  iterate over the result set, you will need a looping construct that
  will further impact performance. For these reasons
  <function>mysqli_fetch_all</function> should only be used in those
  situations where the fetched result set will be sent to another layer
  for processing.
 </para>

 <para>
  <emphasis role="bold">Using Statistical Data</emphasis>
 </para>

 <para>
  MySQL Native Driver contains support for gathering statistics on the
  communication between the client and the server. The statistics
  gathered are of three main types:
 </para>

 <itemizedlist>

  <listitem>
   <para>
    Client statistics
   </para>
  </listitem>

  <listitem>
   <para>
    Connection statistics
   </para>
  </listitem>

  <listitem>
   <para>
    Zval cache statistics
   </para>
  </listitem>

 </itemizedlist>

 <para>
  If you are using the <literal>mysqli</literal> extension, 
  these statistics can be obtained through three API calls:
 </para>

 <itemizedlist>

  <listitem>
   <para>
    <function>mysqli_get_client_stats</function>
   </para>
  </listitem>

  <listitem>
   <para>
    <function>mysqli_get_connection_stats</function>
   </para>
  </listitem>

  <listitem>
   <para>
    <function>mysqli_get_cache_stats</function>
   </para>
  </listitem>

 </itemizedlist>

 <para>
  <emphasis role="bold">Accessing Client Statistics</emphasis>
 </para>

 <para>
  To access client statistics, you need to call
  <function>mysqli_get_client_stats</function>. The function call does
  not require any parameters.
 </para>

 <para>
  The function returns an associative array that contains the name of
  the statistic as the key and the statistical data as the value.
 </para>

 <para>
  Client statistics can also be accessed by calling the
  <function>phpinfo</function> function.
 </para>

<!-- [Table of client statistics] -->

 <para>
  <emphasis role="bold">Accessing Connection Statistics</emphasis>
 </para>

 <para>
  To access connection statistics call
  <function>mysqli_get_connection_stats</function>. This takes the
  database connection handle as the parameter.
 </para>

 <para>
  The function returns an associative array that contains the name of
  the statistic as the key and the statistical data as the value.
 </para>

<!-- [Table of connection statistics] -->

 <para>
  <emphasis role="bold">Accessing Zval Cache Statistics</emphasis>
 </para>

 <para>
  The MySQL Native Driver also collects statistics from its internal
  Zval cache. These statistics can be accessed by calling
  <function>mysqli_get_cache_stat</function>.
 </para>

 <para>
  The Zval cache statistics obtained may lead to a tweaking of
  <filename>php.ini</filename> settings related to the Zval cache,
  resulting in better performance.
 </para>

</chapter>
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