php-doc-en/reference/strings/functions/strtr.xml

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<refentry xmlns="http://docbook.org/ns/docbook" xml:id="function.strtr" xmlns:xlink="http://www.w3.org/1999/xlink">
 <refnamediv>
  <refname>strtr</refname>
  <refpurpose>Translate characters or replace substrings</refpurpose>
 </refnamediv>
 
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>string</type><methodname>strtr</methodname>
   <methodparam><type>string</type><parameter>str</parameter></methodparam>
   <methodparam><type>string</type><parameter>from</parameter></methodparam>
   <methodparam><type>string</type><parameter>to</parameter></methodparam>
  </methodsynopsis>
  <methodsynopsis>
   <type>string</type><methodname>strtr</methodname>
   <methodparam><type>string</type><parameter>str</parameter></methodparam>
   <methodparam><type>array</type><parameter>replace_pairs</parameter></methodparam>
  </methodsynopsis>
  <para>
   If given three arguments, this function returns a copy of
   <parameter>str</parameter> where all occurrences of each (single-byte)
   character in <parameter>from</parameter> have been translated to the
   corresponding character in <parameter>to</parameter>, i.e., every
   occurrence of <literal>$from[$n]</literal> has been replaced with
   <literal>$to[$n]</literal>, where <literal>$n</literal> is a valid
   offset in both arguments.
  </para>
  <para>
   If <parameter>from</parameter> and <parameter>to</parameter> have
   different lengths, the extra characters in the longer of the two
   are ignored. The length of <parameter>str</parameter> will be the same as
   the return value's.
  </para>
  <para>
   If given two arguments, the second should be an <type>array</type> in the
   form <literal>array('from' => 'to', ...)</literal>. The return value is
   a <type>string</type> where all the occurrences of the array keys have been
   replaced by the corresponding values. The longest keys will be tried first.
   Once a substring has been replaced, its new value will not be searched
   again.
  </para>
  <para>
   In this case, the keys and the values may have any length, provided that
   there is no empty key; additionally, the length of the return value may
   differ from that of <parameter>str</parameter>.
   However, this function will be the most efficient when all the keys have the
   same size.
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>str</parameter></term>
     <listitem>
      <para>
       The <type>string</type> being translated.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>from</parameter></term>
     <listitem>
      <para>
       The <type>string</type> being translated to <parameter>to</parameter>.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>to</parameter></term>
     <listitem>
      <para>
       The <type>string</type> replacing <parameter>from</parameter>.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>replace_pairs</parameter></term>
     <listitem>
      <para>
       The <parameter>replace_pairs</parameter> parameter may be used instead of 
       <parameter>to</parameter> and <parameter>from</parameter>, in which case it's an
       <type>array</type> in the form <literal>array('from' => 'to', ...)</literal>. 
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Returns the translated <type>string</type>.
  </para>
  <para>
   If <parameter>replace_pairs</parameter> contains a key which
   is an empty <type>string</type> (<literal>""</literal>),
   &false; will be returned. If the <parameter>str</parameter> is not a scalar
   then it is not typecasted into a string, instead a warning is raised and 
   &null; is returned. 
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>strtr</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
//In this form, strtr() does byte-by-byte translation
//Therefore, we are assuming a single-byte encoding here:
$addr = strtr($addr, "äåö", "aao");
?>
]]>
    </programlisting>
   </example>
  </para>
  <para>
   The next example shows the behavior of <function>strtr</function> when
   called with only two arguments. Note the preference of the replacements
   (<literal>"h"</literal> is not picked because there are longer matches)
   and how replaced text was not searched again.
  </para>
  <example>
   <title><function>strtr</function> example with two arguments</title>
    <programlisting role="php">
<![CDATA[
<?php
$trans = array("h" => "-", "hello" => "hi", "hi" => "hello");
echo strtr("hi all, I said hello", $trans);
?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
hello all, I said hi
]]>
    </screen>
  </example>
  <para>
   The two modes of behavior are substantially different. With three arguments,
   <function>strtr</function> will replace bytes; with two, it may replace
   longer substrings.
  </para>
  <example>
   <title><function>strtr</function> behavior comparison</title>
    <programlisting role="php">
<![CDATA[
<?php
echo strtr("baab", "ab", "01"),"\n";

$trans = array("ab" => "01");
echo strtr("baab", $trans);
?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
1001
ba01
]]>
    </screen>
  </example>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>str_replace</function></member>
    <member><function>preg_replace</function></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>

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