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<div class="refnamediv">
<h1 class="refname">preg_match</h1>
<p class="verinfo">(PHP 4, PHP 5)</p><p class="refpurpose"><span class="refname">preg_match</span> — <span class="dc-title">Perform a regular expression match</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.preg-match-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">int</span> <span class="methodname"><strong>preg_match</strong></span>
( <span class="methodparam"><span class="type">string</span> <code class="parameter">$pattern</code></span>
, <span class="methodparam"><span class="type">string</span> <code class="parameter">$subject</code></span>
[, <span class="methodparam"><span class="type">array</span> <code class="parameter reference">&$matches</code></span>
[, <span class="methodparam"><span class="type">int</span> <code class="parameter">$flags</code><span class="initializer"> = 0</span></span>
[, <span class="methodparam"><span class="type">int</span> <code class="parameter">$offset</code><span class="initializer"> = 0</span></span>
]]] )</div>
<p class="para rdfs-comment">
Searches <em><code class="parameter">subject</code></em> for a match to the regular
expression given in <em><code class="parameter">pattern</code></em>.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.preg-match-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<span class="term"><em><code class="parameter">pattern</code></em></span>
<dd>
<p class="para">
The pattern to search for, as a string.
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">subject</code></em></span>
<dd>
<p class="para">
The input string.
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">matches</code></em></span>
<dd>
<p class="para">
If <em><code class="parameter">matches</code></em> is provided, then it is filled with
the results of search. <var class="varname"><var class="varname">$matches[0]</var></var> will contain the
text that matched the full pattern, <var class="varname"><var class="varname">$matches[1]</var></var>
will have the text that matched the first captured parenthesized
subpattern, and so on.
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">flags</code></em></span>
<dd>
<p class="para">
<em><code class="parameter">flags</code></em> can be the following flag:
<dl>
<dt>
<span class="term"><strong><code>PREG_OFFSET_CAPTURE</code></strong></span>
<dd>
<span class="simpara">
If this flag is passed, for every occurring match the appendant string
offset will also be returned. Note that this changes the value of
<em><code class="parameter">matches</code></em> into an array where every element is an
array consisting of the matched string at offset <em>0</em>
and its string offset into <em><code class="parameter">subject</code></em> at offset
<em>1</em>.
</span>
</dd>
</dt>
</dl>
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">offset</code></em></span>
<dd>
<p class="para">
Normally, the search starts from the beginning of the subject string.
The optional parameter <em><code class="parameter">offset</code></em> can be used to
specify the alternate place from which to start the search (in bytes).
</p>
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
Using <em><code class="parameter">offset</code></em> is not equivalent to passing
<em>substr($subject, $offset)</em> to
<span class="function"><strong>preg_match()</strong></span> in place of the subject string,
because <em><code class="parameter">pattern</code></em> can contain assertions such as
<em class="emphasis">^</em>, <em class="emphasis">$</em> or
<em class="emphasis">(?<=x)</em>. Compare:
<div class="informalexample">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$subject </span><span style="color: #007700">= </span><span style="color: #DD0000">"abcdef"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$pattern </span><span style="color: #007700">= </span><span style="color: #DD0000">'/^def/'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">preg_match</span><span style="color: #007700">(</span><span style="color: #0000BB">$pattern</span><span style="color: #007700">, </span><span style="color: #0000BB">$subject</span><span style="color: #007700">, </span><span style="color: #0000BB">$matches</span><span style="color: #007700">, </span><span style="color: #0000BB">PREG_OFFSET_CAPTURE</span><span style="color: #007700">, </span><span style="color: #0000BB">3</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$matches</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<p class="para">The above example will output:</p>
<div class="example-contents screen">
<div class="cdata"><pre>
Array
(
)
</pre></div>
</div>
<p class="para">
while this example
</p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$subject </span><span style="color: #007700">= </span><span style="color: #DD0000">"abcdef"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$pattern </span><span style="color: #007700">= </span><span style="color: #DD0000">'/^def/'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">preg_match</span><span style="color: #007700">(</span><span style="color: #0000BB">$pattern</span><span style="color: #007700">, </span><span style="color: #0000BB">substr</span><span style="color: #007700">(</span><span style="color: #0000BB">$subject</span><span style="color: #007700">,</span><span style="color: #0000BB">3</span><span style="color: #007700">), </span><span style="color: #0000BB">$matches</span><span style="color: #007700">, </span><span style="color: #0000BB">PREG_OFFSET_CAPTURE</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$matches</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<p class="para">
will produce
</p>
<div class="example-contents screen">
<div class="cdata"><pre>
Array
(
[0] => Array
(
[0] => def
[1] => 0
)
)
</pre></div>
</div>
</div>
</p>
</p></blockquote>
</dd>
</dt>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.preg-match-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
<span class="function"><strong>preg_match()</strong></span> returns 1 if the <em><code class="parameter">pattern</code></em>
matches given <em><code class="parameter">subject</code></em>, 0 if it does not, or <strong><code>FALSE</code></strong>
if an error occurred.
</p>
<div class="warning"><strong class="warning">Warning</strong><p class="simpara">This function may
return Boolean <strong><code>FALSE</code></strong>, but may also return a non-Boolean value which
evaluates to <strong><code>FALSE</code></strong>. Please read the section on <a href="language.types.boolean.html" class="link">Booleans</a> for more
information. Use <a href="language.operators.comparison.html" class="link">the ===
operator</a> for testing the return value of this
function.</p></div>
</div>
<div class="refsect1 changelog" id="refsect1-function.preg-match-changelog">
<h3 class="title">Changelog</h3>
<p class="para">
<table class="doctable informaltable">
<thead>
<tr>
<th>Version</th>
<th>Description</th>
</tr>
</thead>
<tbody class="tbody">
<tr>
<td>5.3.6</td>
<td>
Returns <strong><code>FALSE</code></strong> if <em><code class="parameter">offset</code></em> is higher than
<em><code class="parameter">subject</code></em> length.
</td>
</tr>
<tr>
<td>5.2.2</td>
<td>
Named subpatterns now accept the
syntax <em>(?<name>)</em>
and <em>(?'name')</em> as well
as <em>(?P<name>)</em>. Previous versions
accepted only <em>(?P<name>)</em>.
</td>
</tr>
<tr>
<td>4.3.3</td>
<td>
The <em><code class="parameter">offset</code></em> parameter was added
</td>
</tr>
<tr>
<td>4.3.0</td>
<td>
The <strong><code>PREG_OFFSET_CAPTURE</code></strong> flag was added
</td>
</tr>
<tr>
<td>4.3.0</td>
<td>
The <em><code class="parameter">flags</code></em> parameter was added
</td>
</tr>
</tbody>
</table>
</p>
</div>
<div class="refsect1 examples" id="refsect1-function.preg-match-examples">
<h3 class="title">Examples</h3>
<p class="para">
<div class="example" id="example-4788">
<p><strong>Example #1 Find the string of text "php"</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">// The "i" after the pattern delimiter indicates a case-insensitive search<br /></span><span style="color: #007700">if (</span><span style="color: #0000BB">preg_match</span><span style="color: #007700">(</span><span style="color: #DD0000">"/php/i"</span><span style="color: #007700">, </span><span style="color: #DD0000">"PHP is the web scripting language of choice."</span><span style="color: #007700">)) {<br /> echo </span><span style="color: #DD0000">"A match was found."</span><span style="color: #007700">;<br />} else {<br /> echo </span><span style="color: #DD0000">"A match was not found."</span><span style="color: #007700">;<br />}<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
<p class="para">
<div class="example" id="example-4789">
<p><strong>Example #2 Find the word "web"</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">/* The \b in the pattern indicates a word boundary, so only the distinct<br /> * word "web" is matched, and not a word partial like "webbing" or "cobweb" */<br /></span><span style="color: #007700">if (</span><span style="color: #0000BB">preg_match</span><span style="color: #007700">(</span><span style="color: #DD0000">"/\bweb\b/i"</span><span style="color: #007700">, </span><span style="color: #DD0000">"PHP is the web scripting language of choice."</span><span style="color: #007700">)) {<br /> echo </span><span style="color: #DD0000">"A match was found."</span><span style="color: #007700">;<br />} else {<br /> echo </span><span style="color: #DD0000">"A match was not found."</span><span style="color: #007700">;<br />}<br /><br />if (</span><span style="color: #0000BB">preg_match</span><span style="color: #007700">(</span><span style="color: #DD0000">"/\bweb\b/i"</span><span style="color: #007700">, </span><span style="color: #DD0000">"PHP is the website scripting language of choice."</span><span style="color: #007700">)) {<br /> echo </span><span style="color: #DD0000">"A match was found."</span><span style="color: #007700">;<br />} else {<br /> echo </span><span style="color: #DD0000">"A match was not found."</span><span style="color: #007700">;<br />}<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
<p class="para">
<div class="example" id="example-4790">
<p><strong>Example #3 Getting the domain name out of a URL</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">// get host name from URL<br /></span><span style="color: #0000BB">preg_match</span><span style="color: #007700">(</span><span style="color: #DD0000">'@^(?:http://)?([^/]+)@i'</span><span style="color: #007700">,<br /> </span><span style="color: #DD0000">"http://www.php.net/index.html"</span><span style="color: #007700">, </span><span style="color: #0000BB">$matches</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$host </span><span style="color: #007700">= </span><span style="color: #0000BB">$matches</span><span style="color: #007700">[</span><span style="color: #0000BB">1</span><span style="color: #007700">];<br /><br /></span><span style="color: #FF8000">// get last two segments of host name<br /></span><span style="color: #0000BB">preg_match</span><span style="color: #007700">(</span><span style="color: #DD0000">'/[^.]+\.[^.]+$/'</span><span style="color: #007700">, </span><span style="color: #0000BB">$host</span><span style="color: #007700">, </span><span style="color: #0000BB">$matches</span><span style="color: #007700">);<br />echo </span><span style="color: #DD0000">"domain name is: </span><span style="color: #007700">{</span><span style="color: #0000BB">$matches</span><span style="color: #007700">[</span><span style="color: #0000BB">0</span><span style="color: #007700">]}</span><span style="color: #DD0000">\n"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
domain name is: php.net
</pre></div>
</div>
</div>
</p>
<p class="para">
<div class="example" id="example-4791">
<p><strong>Example #4 Using named subpattern</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br />$str </span><span style="color: #007700">= </span><span style="color: #DD0000">'foobar: 2008'</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">preg_match</span><span style="color: #007700">(</span><span style="color: #DD0000">'/(?P<name>\w+): (?P<digit>\d+)/'</span><span style="color: #007700">, </span><span style="color: #0000BB">$str</span><span style="color: #007700">, </span><span style="color: #0000BB">$matches</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">/* This also works in PHP 5.2.2 (PCRE 7.0) and later, however <br /> * the above form is recommended for backwards compatibility */<br />// preg_match('/(?<name>\w+): (?<digit>\d+)/', $str, $matches);<br /><br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$matches</span><span style="color: #007700">);<br /><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>
Array
(
[0] => foobar: 2008
[name] => foobar
[1] => foobar
[digit] => 2008
[2] => 2008
)
</pre></div>
</div>
</div>
</p>
</div>
<div class="refsect1 notes" id="refsect1-function.preg-match-notes">
<h3 class="title">Notes</h3>
<div class="tip"><strong class="tip">Tip</strong>
<p class="para">
Do not use <span class="function"><strong>preg_match()</strong></span> if you only want to check if
one string is contained in another string. Use
<span class="function"><a href="function.strpos.html" class="function">strpos()</a></span> or <span class="function"><a href="function.strstr.html" class="function">strstr()</a></span> instead as
they will be faster.
</p>
</div>
</div>
<div class="refsect1 seealso" id="refsect1-function.preg-match-seealso">
<h3 class="title">See Also</h3>
<p class="para">
<ul class="simplelist">
<li class="member"><a href="pcre.pattern.html" class="link">PCRE Patterns</a></li>
<li class="member"> <span class="function"><a href="function.preg-match-all.html" class="function" rel="rdfs-seeAlso">preg_match_all()</a> - Perform a global regular expression match</span></li>
<li class="member"> <span class="function"><a href="function.preg-replace.html" class="function" rel="rdfs-seeAlso">preg_replace()</a> - Perform a regular expression search and replace</span></li>
<li class="member"> <span class="function"><a href="function.preg-split.html" class="function" rel="rdfs-seeAlso">preg_split()</a> - Split string by a regular expression</span></li>
<li class="member"> <span class="function"><a href="function.preg-last-error.html" class="function" rel="rdfs-seeAlso">preg_last_error()</a> - Returns the error code of the last PCRE regex execution</span></li>
</ul>
</p>
</div>
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