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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision: 290982 $ -->
<chapter xml:id="array.sorting" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
<title>Sorting Arrays</title>
<para>
PHP has several functions that deal with sorting arrays, and this
document exists to help sort it all out.
</para>
<para>
The main differences are:
</para>
<para>
<simplelist>
<member>
Some sort based on the <type>array</type> keys, whereas others by
the values: <literal>$array['key'] = 'value';</literal>
</member>
<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 ...)
</member>
<member>
The order of the sort: alphabetical, low to high (ascending),
high to low (descending), numerical, natural, random, or user defined
</member>
<member>
Note: All of these sort functions act directly on the array
variable itself, as opposed to returning a new sorted array
</member>
<member>
If any of these sort functions evaluates two members as equal then the
order is undefined (the sorting is not stable).
</member>
</simplelist>
</para>
<para>
<table>
<title>Sorting function attributes</title>
<tgroup cols="5">
<thead>
<row>
<entry>Function name</entry>
<entry>Sorts by</entry>
<entry>Maintains key association</entry>
<entry>Order of sort</entry>
<entry>Related functions</entry>
</row>
</thead>
<tbody>
<row>
<entry><function>array_multisort</function></entry>
<entry>value</entry>
<entry>associative yes, numeric no</entry>
<entry>first array or sort options</entry>
<entry><function>array_walk</function></entry>
</row>
<row>
<entry><function>asort</function></entry>
<entry>value</entry>
<entry>yes</entry>
<entry>low to high</entry>
<entry><function>arsort</function></entry>
</row>
<row>
<entry><function>arsort</function></entry>
<entry>value</entry>
<entry>yes</entry>
<entry>high to low</entry>
<entry><function>asort</function></entry>
</row>
<row>
<entry><function>krsort</function></entry>
<entry>key</entry>
<entry>yes</entry>
<entry>high to low</entry>
<entry><function>ksort</function></entry>
</row>
<row>
<entry><function>ksort</function></entry>
<entry>key</entry>
<entry>yes</entry>
<entry>low to high</entry>
<entry><function>asort</function></entry>
</row>
<row>
<entry><function>natcasesort</function></entry>
<entry>value</entry>
<entry>yes</entry>
<entry>natural, case insensitive</entry>
<entry><function>natsort</function></entry>
</row>
<row>
<entry><function>natsort</function></entry>
<entry>value</entry>
<entry>yes</entry>
<entry>natural</entry>
<entry><function>natcasesort</function></entry>
</row>
<row>
<entry><function>rsort</function></entry>
<entry>value</entry>
<entry>no</entry>
<entry>high to low</entry>
<entry><function>sort</function></entry>
</row>
<row>
<entry><function>shuffle</function></entry>
<entry>value</entry>
<entry>no</entry>
<entry>random</entry>
<entry><function>array_rand</function></entry>
</row>
<row>
<entry><function>sort</function></entry>
<entry>value</entry>
<entry>no</entry>
<entry>low to high</entry>
<entry><function>rsort</function></entry>
</row>
<row>
<entry><function>uasort</function></entry>
<entry>value</entry>
<entry>yes</entry>
<entry>user defined</entry>
<entry><function>uksort</function></entry>
</row>
<row>
<entry><function>uksort</function></entry>
<entry>key</entry>
<entry>yes</entry>
<entry>user defined</entry>
<entry><function>uasort</function></entry>
</row>
<row>
<entry><function>usort</function></entry>
<entry>value</entry>
<entry>no</entry>
<entry>user defined</entry>
<entry><function>uasort</function></entry>
</row>
</tbody>
</tgroup>
</table>
</para>
</chapter>
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