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<title>String comparisons using a "natural order" algorithm</title>
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<h1 class="refname">strnatcmp</h1>
<p class="verinfo">(PHP 4, PHP 5)</p><p class="refpurpose"><span class="refname">strnatcmp</span> — <span class="dc-title">String comparisons using a "natural order" algorithm</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.strnatcmp-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">int</span> <span class="methodname"><strong>strnatcmp</strong></span>
( <span class="methodparam"><span class="type">string</span> <code class="parameter">$str1</code></span>
, <span class="methodparam"><span class="type">string</span> <code class="parameter">$str2</code></span>
)</div>
<p class="para rdfs-comment">
This function implements a comparison algorithm that orders
alphanumeric strings in the way a human being would, this is
described as a "natural ordering".
Note that this comparison is case sensitive.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.strnatcmp-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<span class="term"><em><code class="parameter">str1</code></em></span>
<dd>
<p class="para">
The first string.
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">str2</code></em></span>
<dd>
<p class="para">
The second string.
</p>
</dd>
</dt>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.strnatcmp-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Similar to other string comparison functions, this one returns < 0 if
<em><code class="parameter">str1</code></em> is less than <em><code class="parameter">str2</code></em>; >
0 if <em><code class="parameter">str1</code></em> is greater than
<em><code class="parameter">str2</code></em>, and 0 if they are equal.
</p>
</div>
<div class="refsect1 examples" id="refsect1-function.strnatcmp-examples">
<h3 class="title">Examples</h3>
<p class="para">
An example of the difference between this algorithm and the regular
computer string sorting algorithms (used in <span class="function"><a href="function.strcmp.html" class="function">strcmp()</a></span>)
can be seen below:
<div class="informalexample">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$arr1 </span><span style="color: #007700">= </span><span style="color: #0000BB">$arr2 </span><span style="color: #007700">= array(</span><span style="color: #DD0000">"img12.png"</span><span style="color: #007700">, </span><span style="color: #DD0000">"img10.png"</span><span style="color: #007700">, </span><span style="color: #DD0000">"img2.png"</span><span style="color: #007700">, </span><span style="color: #DD0000">"img1.png"</span><span style="color: #007700">);<br />echo </span><span style="color: #DD0000">"Standard string comparison\n"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">usort</span><span style="color: #007700">(</span><span style="color: #0000BB">$arr1</span><span style="color: #007700">, </span><span style="color: #DD0000">"strcmp"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$arr1</span><span style="color: #007700">);<br />echo </span><span style="color: #DD0000">"\nNatural order string comparison\n"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">usort</span><span style="color: #007700">(</span><span style="color: #0000BB">$arr2</span><span style="color: #007700">, </span><span style="color: #DD0000">"strnatcmp"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$arr2</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>
Standard string comparison
Array
(
[0] => img1.png
[1] => img10.png
[2] => img12.png
[3] => img2.png
)
Natural order string comparison
Array
(
[0] => img1.png
[1] => img2.png
[2] => img10.png
[3] => img12.png
)
</pre></div>
</div>
</div>
For more information see: Martin Pool's <a href="http://sourcefrog.net/projects/natsort/" class="link external">» Natural Order String Comparison</a>
page.
</p>
</div>
<div class="refsect1 seealso" id="refsect1-function.strnatcmp-seealso">
<h3 class="title">See Also</h3>
<p class="para">
<ul class="simplelist">
<li class="member"> <span class="function"><a href="function.preg-match.html" class="function" rel="rdfs-seeAlso">preg_match()</a> - Perform a regular expression match</span></li>
<li class="member"> <span class="function"><a href="function.strcasecmp.html" class="function" rel="rdfs-seeAlso">strcasecmp()</a> - Binary safe case-insensitive string comparison</span></li>
<li class="member"> <span class="function"><a href="function.substr.html" class="function" rel="rdfs-seeAlso">substr()</a> - Return part of a string</span></li>
<li class="member"> <span class="function"><a href="function.stristr.html" class="function" rel="rdfs-seeAlso">stristr()</a> - Case-insensitive strstr</span></li>
<li class="member"> <span class="function"><a href="function.strcmp.html" class="function" rel="rdfs-seeAlso">strcmp()</a> - Binary safe string comparison</span></li>
<li class="member"> <span class="function"><a href="function.strncmp.html" class="function" rel="rdfs-seeAlso">strncmp()</a> - Binary safe string comparison of the first n characters</span></li>
<li class="member"> <span class="function"><a href="function.strncasecmp.html" class="function" rel="rdfs-seeAlso">strncasecmp()</a> - Binary safe case-insensitive string comparison of the first n characters</span></li>
<li class="member"> <span class="function"><a href="function.strnatcasecmp.html" class="function" rel="rdfs-seeAlso">strnatcasecmp()</a> - Case insensitive string comparisons using a "natural order" algorithm</span></li>
<li class="member"> <span class="function"><a href="function.strstr.html" class="function" rel="rdfs-seeAlso">strstr()</a> - Find the first occurrence of a string</span></li>
<li class="member"> <span class="function"><a href="function.natsort.html" class="function" rel="rdfs-seeAlso">natsort()</a> - Sort an array using a "natural order" algorithm</span></li>
<li class="member"> <span class="function"><a href="function.natcasesort.html" class="function" rel="rdfs-seeAlso">natcasesort()</a> - Sort an array using a case insensitive "natural order" algorithm</span></li>
</ul>
</p>
</div>
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