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<title>Sort an array using a "natural order" algorithm</title>
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<div class="refnamediv">
<h1 class="refname">natsort</h1>
<p class="verinfo">(PHP 4, PHP 5)</p><p class="refpurpose"><span class="refname">natsort</span> — <span class="dc-title">Sort an array using a "natural order" algorithm</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.natsort-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">bool</span> <span class="methodname"><strong>natsort</strong></span>
( <span class="methodparam"><span class="type">array</span> <code class="parameter reference">&$array</code></span>
)</div>
<p class="para rdfs-comment">
This function implements a sort algorithm that orders alphanumeric strings
in the way a human being would while maintaining key/value associations.
This is described as a "natural ordering". An example of the difference
between this algorithm and the regular computer string sorting algorithms
(used in <span class="function"><a href="function.sort.html" class="function">sort()</a></span>) can be seen in the example below.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.natsort-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<span class="term"><em><code class="parameter">array</code></em></span>
<dd>
<p class="para">
The input array.
</p>
</dd>
</dt>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.natsort-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Returns <strong><code>TRUE</code></strong> on success or <strong><code>FALSE</code></strong> on failure.
</p>
</div>
<div class="refsect1 changelog" id="refsect1-function.natsort-changelog">
<h3 class="title">Changelog</h3>
<table class="doctable informaltable">
<thead>
<tr>
<th>Version</th>
<th>Description</th>
</tr>
</thead>
<tbody class="tbody">
<tr>
<td>5.2.10</td>
<td>
Zero padded numeric strings (e.g., '00005') now essentially ignore the 0 padding.
</td>
</tr>
</tbody>
</table>
</div>
<div class="refsect1 examples" id="refsect1-function.natsort-examples">
<h3 class="title">Examples</h3>
<p class="para">
<div class="example" id="example-5024">
<p><strong>Example #1 <span class="function"><strong>natsort()</strong></span> examples demonstrating basic usage</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$array1 </span><span style="color: #007700">= </span><span style="color: #0000BB">$array2 </span><span style="color: #007700">= array(</span><span style="color: #DD0000">"img12.png"</span><span style="color: #007700">, </span><span style="color: #DD0000">"img10.png"</span><span style="color: #007700">, </span><span style="color: #DD0000">"img2.png"</span><span style="color: #007700">, </span><span style="color: #DD0000">"img1.png"</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">asort</span><span style="color: #007700">(</span><span style="color: #0000BB">$array1</span><span style="color: #007700">);<br />echo </span><span style="color: #DD0000">"Standard sorting\n"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$array1</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">natsort</span><span style="color: #007700">(</span><span style="color: #0000BB">$array2</span><span style="color: #007700">);<br />echo </span><span style="color: #DD0000">"\nNatural order sorting\n"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$array2</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
Standard sorting
Array
(
[3] => img1.png
[1] => img10.png
[0] => img12.png
[2] => img2.png
)
Natural order sorting
Array
(
[3] => img1.png
[2] => img2.png
[1] => img10.png
[0] => img12.png
)
</pre></div>
</div>
<div class="example-contents"><p>
For more information see: Martin Pool's <a href="http://sourcefrog.net/projects/natsort/" class="link external">» Natural Order String Comparison</a>
page.
</p></div>
</div>
<div class="example" id="example-5025">
<p><strong>Example #2 <span class="function"><strong>natsort()</strong></span> examples demonstrating potential gotchas</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">echo </span><span style="color: #DD0000">"Negative numbers\n"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$negative </span><span style="color: #007700">= array(</span><span style="color: #DD0000">'-5'</span><span style="color: #007700">,</span><span style="color: #DD0000">'3'</span><span style="color: #007700">,</span><span style="color: #DD0000">'-2'</span><span style="color: #007700">,</span><span style="color: #DD0000">'0'</span><span style="color: #007700">,</span><span style="color: #DD0000">'-1000'</span><span style="color: #007700">,</span><span style="color: #DD0000">'9'</span><span style="color: #007700">,</span><span style="color: #DD0000">'1'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$negative</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">natsort</span><span style="color: #007700">(</span><span style="color: #0000BB">$negative</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$negative</span><span style="color: #007700">);<br /><br />echo </span><span style="color: #DD0000">"Zero padding\n"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$zeros </span><span style="color: #007700">= array(</span><span style="color: #DD0000">'09'</span><span style="color: #007700">, </span><span style="color: #DD0000">'8'</span><span style="color: #007700">, </span><span style="color: #DD0000">'10'</span><span style="color: #007700">, </span><span style="color: #DD0000">'009'</span><span style="color: #007700">, </span><span style="color: #DD0000">'011'</span><span style="color: #007700">, </span><span style="color: #DD0000">'0'</span><span style="color: #007700">); <br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$zeros</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">natsort</span><span style="color: #007700">(</span><span style="color: #0000BB">$zeros</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$zeros</span><span style="color: #007700">);<br /><br />echo </span><span style="color: #DD0000">"Other characters interfering\n"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$images_oops </span><span style="color: #007700">= array(</span><span style="color: #DD0000">'image_1.jpg'</span><span style="color: #007700">,</span><span style="color: #DD0000">'image_12.jpg'</span><span style="color: #007700">, </span><span style="color: #DD0000">'image_21.jpg'</span><span style="color: #007700">, </span><span style="color: #DD0000">'image_4.jpg'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$images_oops</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">natsort</span><span style="color: #007700">(</span><span style="color: #0000BB">$images_oops</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$images_oops</span><span style="color: #007700">);<br /><br />echo </span><span style="color: #DD0000">"Sort by keys\n"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$smoothie </span><span style="color: #007700">= array(</span><span style="color: #DD0000">'orange' </span><span style="color: #007700">=> </span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #DD0000">'apple' </span><span style="color: #007700">=> </span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #DD0000">'yogurt' </span><span style="color: #007700">=> </span><span style="color: #0000BB">4</span><span style="color: #007700">, </span><span style="color: #DD0000">'banana' </span><span style="color: #007700">=> </span><span style="color: #0000BB">4</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$smoothie</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">uksort</span><span style="color: #007700">( </span><span style="color: #0000BB">$smoothie</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">$smoothie</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>
Negative numbers
Array
(
[0] => -5
[1] => 3
[2] => -2
[3] => 0
[4] => -1000
[5] => 9
[6] => 1
)
Array
(
[2] => -2
[0] => -5
[4] => -1000
[3] => 0
[6] => 1
[1] => 3
[5] => 9
)
Zero padding
Array
(
[0] => 09
[1] => 8
[2] => 10
[3] => 009
[4] => 011
[5] => 0
)
Array
(
[5] => 0
[1] => 8
[3] => 009
[0] => 09
[2] => 10
[4] => 011
)
Other characters interfering
Array
(
[0] => image_1.jpg
[1] => image_12.jpg
[2] => image_21.jpg
[3] => image_4.jpg
)
Array
(
[0] => image_1.jpg
[3] => image_4.jpg
[1] => image_12.jpg
[2] => image_21.jpg
)
Sort by keys
Array
(
[orange] => 1
[apple] => 1
[yogurt] => 4
[banana] => 4
)
Array
(
[apple] => 1
[banana] => 4
[orange] => 1
[yogurt] => 4
)
</pre></div>
</div>
</div>
</p>
</div>
<div class="refsect1 seealso" id="refsect1-function.natsort-seealso">
<h3 class="title">See Also</h3>
<p class="para">
<ul class="simplelist">
<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>
<li class="member">The <a href="array.sorting.html" class="link">comparison of array sorting functions</a></li>
<li class="member"> <span class="function"><a href="function.strnatcmp.html" class="function" rel="rdfs-seeAlso">strnatcmp()</a> - String comparisons using a "natural order" algorithm</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>
</ul>
</p>
</div>
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