doc-en/reference/array/sorting.xml at master · php/doc-en · GitHub

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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->

<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, ascending (low to high),
    descending (high to low), 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 they retain their original order.
    Prior to PHP 8.0.0, their order were undefined (the sorting was 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><type>string</type> keys yes, <type>int</type> keys 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>ascending</entry>
      <entry><function>arsort</function></entry>
     </row>
     <row>
      <entry><function>arsort</function></entry>
      <entry>value</entry>
      <entry>yes</entry>
      <entry>descending</entry>
      <entry><function>asort</function></entry>
     </row>
     <row>
      <entry><function>krsort</function></entry>
      <entry>key</entry>
      <entry>yes</entry>
      <entry>descending</entry>
      <entry><function>ksort</function></entry>
     </row>
     <row>
      <entry><function>ksort</function></entry>
      <entry>key</entry>
      <entry>yes</entry>
      <entry>ascending</entry>
      <entry><function>krsort</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>descending</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>ascending</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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