php-doc-en/reference/array/functions/array-flip.xml

<?xml version="1.0" encoding="utf-8"?>
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<refentry xmlns="http://docbook.org/ns/docbook" xml:id="function.array-flip">
 <refnamediv>
  <refname>array_flip</refname>
  <refpurpose>Exchanges all keys with their associated values in an array</refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>array</type><methodname>array_flip</methodname>
   <methodparam><type>array</type><parameter>trans</parameter></methodparam>
  </methodsynopsis>
  <para>
   <function>array_flip</function> returns an <type>array</type> in flip
   order, i.e. keys from <parameter>trans</parameter> become values and values
   from <parameter>trans</parameter> become keys.
  </para>
  <para>
   Note that the values of <parameter>trans</parameter> need to be valid
   keys, i.e. they need to be either <type>integer</type> or
   <type>string</type>. A warning will be emitted if a value has the wrong
   type, and the key/value pair in question <emphasis>will not be
   flipped</emphasis>.
  </para>
  <para>
   If a value has several occurrences, the latest key will be
   used as its values, and all others will be lost.
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>trans</parameter></term>
     <listitem>
      <para>
       An array of key/value pairs to be flipped.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Returns the flipped array on success and &null; on failure.
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>array_flip</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
$trans = array_flip($trans);
$original = strtr($str, $trans);
?>
]]>
    </programlisting>
   </example>
  </para>
  <para>
   <example>
    <title><function>array_flip</function> example : collision</title>
    <programlisting role="php">
<![CDATA[
<?php
$trans = array("a" => 1, "b" => 1, "c" => 2);
$trans = array_flip($trans);
print_r($trans);
?>
]]>
    </programlisting>
    <para>
     now <varname>$trans</varname> is:
    </para>
    <screen>
<![CDATA[
Array
(
    [1] => b
    [2] => c
)
]]>
    </screen>
   </example>
  </para>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>array_values</function></member>
    <member><function>array_keys</function></member>
    <member><function>array_reverse</function></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>

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