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

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<!-- splitted from ./en/functions/array.xml, last change in rev 1.107 -->
  <refentry id="function.array-flip">
   <refnamediv>
    <refname>array_flip</refname>
    <refpurpose>Exchanges all keys with their associated values in an array</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <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>
    <para>
     <function>array_flip</function> returns &false;
     if it fails.
    </para>
    <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>
    <para>
     See also <function>array_values</function>,
     <function>array_keys</function>, and
     <function>array_reverse</function>.
    </para>
   </refsect1>
  </refentry>

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