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<h1>Sorting Arrays</h1>
<p class="para">
PHP has several functions that deal with sorting arrays, and this
document exists to help sort it all out.
</p>
<p class="para">
The main differences are:
</p>
<p class="para">
<ul class="simplelist">
<li class="member">
Some sort based on the <span class="type"><a href="language.types.array.html" class="type array">array</a></span> keys, whereas others by
the values: <em>$array['key'] = 'value';</em>
</li>
<li class="member">
Whether or not the correlation between the keys and values are
maintained after the sort, which may mean the keys are reset
numerically (0,1,2 ...)
</li>
<li class="member">
The order of the sort: alphabetical, low to high (ascending),
high to low (descending), numerical, natural, random, or user defined
</li>
<li class="member">
Note: All of these sort functions act directly on the array
variable itself, as opposed to returning a new sorted array
</li>
<li class="member">
If any of these sort functions evaluates two members as equal then the
order is undefined (the sorting is not stable).
</li>
</ul>
</p>
<p class="para">
<table class="doctable table">
<caption><strong>Sorting function attributes</strong></caption>
<thead>
<tr>
<th>Function name</th>
<th>Sorts by</th>
<th>Maintains key association</th>
<th>Order of sort</th>
<th>Related functions</th>
</tr>
</thead>
<tbody class="tbody">
<tr>
<td> <span class="function"><a href="function.array-multisort.html" class="function">array_multisort()</a></span></td>
<td>value</td>
<td>associative yes, numeric no</td>
<td>first array or sort options</td>
<td> <span class="function"><a href="function.array-walk.html" class="function">array_walk()</a></span></td>
</tr>
<tr>
<td> <span class="function"><a href="function.asort.html" class="function">asort()</a></span></td>
<td>value</td>
<td>yes</td>
<td>low to high</td>
<td> <span class="function"><a href="function.arsort.html" class="function">arsort()</a></span></td>
</tr>
<tr>
<td> <span class="function"><a href="function.arsort.html" class="function">arsort()</a></span></td>
<td>value</td>
<td>yes</td>
<td>high to low</td>
<td> <span class="function"><a href="function.asort.html" class="function">asort()</a></span></td>
</tr>
<tr>
<td> <span class="function"><a href="function.krsort.html" class="function">krsort()</a></span></td>
<td>key</td>
<td>yes</td>
<td>high to low</td>
<td> <span class="function"><a href="function.ksort.html" class="function">ksort()</a></span></td>
</tr>
<tr>
<td> <span class="function"><a href="function.ksort.html" class="function">ksort()</a></span></td>
<td>key</td>
<td>yes</td>
<td>low to high</td>
<td> <span class="function"><a href="function.asort.html" class="function">asort()</a></span></td>
</tr>
<tr>
<td> <span class="function"><a href="function.natcasesort.html" class="function">natcasesort()</a></span></td>
<td>value</td>
<td>yes</td>
<td>natural, case insensitive</td>
<td> <span class="function"><a href="function.natsort.html" class="function">natsort()</a></span></td>
</tr>
<tr>
<td> <span class="function"><a href="function.natsort.html" class="function">natsort()</a></span></td>
<td>value</td>
<td>yes</td>
<td>natural</td>
<td> <span class="function"><a href="function.natcasesort.html" class="function">natcasesort()</a></span></td>
</tr>
<tr>
<td> <span class="function"><a href="function.rsort.html" class="function">rsort()</a></span></td>
<td>value</td>
<td>no</td>
<td>high to low</td>
<td> <span class="function"><a href="function.sort.html" class="function">sort()</a></span></td>
</tr>
<tr>
<td> <span class="function"><a href="function.shuffle.html" class="function">shuffle()</a></span></td>
<td>value</td>
<td>no</td>
<td>random</td>
<td> <span class="function"><a href="function.array-rand.html" class="function">array_rand()</a></span></td>
</tr>
<tr>
<td> <span class="function"><a href="function.sort.html" class="function">sort()</a></span></td>
<td>value</td>
<td>no</td>
<td>low to high</td>
<td> <span class="function"><a href="function.rsort.html" class="function">rsort()</a></span></td>
</tr>
<tr>
<td> <span class="function"><a href="function.uasort.html" class="function">uasort()</a></span></td>
<td>value</td>
<td>yes</td>
<td>user defined</td>
<td> <span class="function"><a href="function.uksort.html" class="function">uksort()</a></span></td>
</tr>
<tr>
<td> <span class="function"><a href="function.uksort.html" class="function">uksort()</a></span></td>
<td>key</td>
<td>yes</td>
<td>user defined</td>
<td> <span class="function"><a href="function.uasort.html" class="function">uasort()</a></span></td>
</tr>
<tr>
<td> <span class="function"><a href="function.usort.html" class="function">usort()</a></span></td>
<td>value</td>
<td>no</td>
<td>user defined</td>
<td> <span class="function"><a href="function.uasort.html" class="function">uasort()</a></span></td>
</tr>
</tbody>
</table>
</p>
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