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<h2 class="title">How it works</h2>
<p class="para">
This describes the background and inner workings of the mysqlnd_uh
extension.
</p>
<p class="para">
Two classes are provided by the extension: <a href="class.mysqlnduhconnection.html" class="classname">MysqlndUhConnection</a>
and <a href="class.mysqlnduhpreparedstatement.html" class="classname">MysqlndUhPreparedStatement</a>. <a href="class.mysqlnduhconnection.html" class="classname">MysqlndUhConnection</a> lets
you access almost all methods of the <em>mysqlnd</em>
internal <em>connection</em> class. The latter exposes some selected
methods of the <em>mysqlnd</em> internal <em>statement</em> class.
For example, <span class="methodname"><a href="mysqlnduhconnection.connect.html" class="methodname">MysqlndUhConnection::connect()</a></span> maps to
the <em>mysqlnd</em> library C function
<em>mysqlnd_conn__connect</em>.
</p>
<p class="para">
As a mysqlnd plugin, the PECL/mysqlnd_uh extension replaces <em>mysqlnd</em>
library C functions with its own functions. Whenever a
PHP MySQL extension compiled to use <em>mysqlnd</em> calls
a mysqlnd function, the functions installed by the plugin are executed
instead of the original <em>mysqlnd</em> ones. For example,
<span class="function"><a href="function.mysqli-connect.html" class="function">mysqli_connect()</a></span> invokes <em>mysqlnd_conn__connect</em>,
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.
</p>
<p class="para">
The built-in PHP classes and their methods do nothing but call their
<em>mysqlnd</em> C library counterparts, to behave exactly
like the original <em>mysqlnd</em> function they replace.
The code below illustrates in pseudo-code what the extension does.
</p>
<p class="para">
<div class="example" id="example-1871">
<p><strong>Example #1 Pseudo-code: what a built-in class does</strong></p>
<div class="example-contents">
<div class="cdata"><pre>
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, ...));
}
}
</pre></div>
</div>
</div>
</p>
<p class="para">
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
<a href="class.mysqlnduhconnection.html" class="classname">MysqlndUhConnection</a> or
<a href="class.mysqlnduhpreparedstatement.html" class="classname">MysqlndUhPreparedStatement</a> to extend the functionality
of the proxy, followed by registering a new proxy object.
Proxy objects are installed by
<span class="function"><a href="function.mysqlnd-uh-set-connection-proxy.html" class="function">mysqlnd_uh_set_connection_proxy()</a></span>
and
<span class="function"><a href="function.mysqlnd-uh-set-statement-proxy.html" class="function">mysqlnd_uh_set_statement_proxy()</a></span>.
</p>
<p class="para">
<div class="example" id="example-1872">
<p><strong>Example #2 Installing a proxy</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">class </span><span style="color: #0000BB">proxy </span><span style="color: #007700">extends </span><span style="color: #0000BB">MysqlndUhConnection </span><span style="color: #007700">{<br /> public function </span><span style="color: #0000BB">connect</span><span style="color: #007700">(</span><span style="color: #0000BB">$res</span><span style="color: #007700">, </span><span style="color: #0000BB">$host</span><span style="color: #007700">, </span><span style="color: #0000BB">$user</span><span style="color: #007700">, </span><span style="color: #0000BB">$passwd</span><span style="color: #007700">, </span><span style="color: #0000BB">$db</span><span style="color: #007700">, </span><span style="color: #0000BB">$port</span><span style="color: #007700">, </span><span style="color: #0000BB">$socket</span><span style="color: #007700">, </span><span style="color: #0000BB">$mysql_flags</span><span style="color: #007700">) {<br /> </span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"%s(%s)\n"</span><span style="color: #007700">, </span><span style="color: #0000BB">__METHOD__</span><span style="color: #007700">, </span><span style="color: #0000BB">var_export</span><span style="color: #007700">(</span><span style="color: #0000BB">func_get_args</span><span style="color: #007700">(), </span><span style="color: #0000BB">true</span><span style="color: #007700">));<br /> </span><span style="color: #0000BB">$ret </span><span style="color: #007700">= </span><span style="color: #0000BB">parent</span><span style="color: #007700">::</span><span style="color: #0000BB">connect</span><span style="color: #007700">(</span><span style="color: #0000BB">$res</span><span style="color: #007700">, </span><span style="color: #0000BB">$host</span><span style="color: #007700">, </span><span style="color: #0000BB">$user</span><span style="color: #007700">, </span><span style="color: #0000BB">$passwd</span><span style="color: #007700">, </span><span style="color: #0000BB">$db</span><span style="color: #007700">, </span><span style="color: #0000BB">$port</span><span style="color: #007700">, </span><span style="color: #0000BB">$socket</span><span style="color: #007700">, </span><span style="color: #0000BB">$mysql_flags</span><span style="color: #007700">);<br /> </span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"%s returns %s\n"</span><span style="color: #007700">, </span><span style="color: #0000BB">__METHOD__</span><span style="color: #007700">, </span><span style="color: #0000BB">var_export</span><span style="color: #007700">(</span><span style="color: #0000BB">$ret</span><span style="color: #007700">, </span><span style="color: #0000BB">true</span><span style="color: #007700">));<br /> return </span><span style="color: #0000BB">$ret</span><span style="color: #007700">;<br /> }<br />}<br /></span><span style="color: #0000BB">mysqlnd_uh_set_connection_proxy</span><span style="color: #007700">(new </span><span style="color: #0000BB">proxy</span><span style="color: #007700">());<br /><br /></span><span style="color: #0000BB">$mysqli </span><span style="color: #007700">= new </span><span style="color: #0000BB">mysqli</span><span style="color: #007700">(</span><span style="color: #DD0000">"localhost"</span><span style="color: #007700">, </span><span style="color: #DD0000">"root"</span><span style="color: #007700">, </span><span style="color: #DD0000">""</span><span style="color: #007700">, </span><span style="color: #DD0000">"test"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
proxy::connect(array (
0 => NULL,
1 => 'localhost',
2 => 'root',
3 => '',
4 => 'test',
5 => 3306,
6 => NULL,
7 => 131072,
))
proxy::connect returns true
</pre></div>
</div>
</div>
</p>
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