strtr

Description

Alternative signature (not supported with named arguments):

If given three arguments, this function returns a copy of string where all occurrences of each (single-byte) character in from have been translated to the corresponding character in to, i.e., every occurrence of $from[$n] has been replaced with $to[$n], where $n is a valid offset in both arguments.

If from and to have different lengths, the extra characters in the longer of the two are ignored. The length of string will be the same as the return value's.

If given two arguments, the second should be an array in the form array('from' => 'to', ...). The return value is a string where all the occurrences of the array keys have been replaced by the corresponding values.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.

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 string. However, this function will be the most efficient when all the keys have the same size.

Parameters

string

The string being translated.

from

The string being translated to to.

to

The string replacing from.

replace_pairs

The replace_pairs parameter may be used instead of to and from, in which case it's an array in the form array('from' => 'to', ...).

If replace_pairs contains a key which is an empty string (""), the element is ignored; as of PHP 8.0.0 E_WARNING is raised in this case.

Return Values

Returns the translated string.

Examples

strtr() example

<?php

$original = "He1Lo, w0rld!";

// With three arguments, strtr() performs byte-by-byte translation.
$result = strtr($original, "1L0", "llo");
echo $result;

The above example will output:

Hello, world!

The next example shows the behavior of strtr() when called with only two arguments. Note the preference of the replacements ("h" is not picked because there are longer matches) and how replaced text was not searched again.

strtr() example with two arguments

<?php

$replace_pairs = ["h" => "-", "hello" => "hi", "hi" => "hello"];
echo strtr("hi all, I said hello", $replace_pairs);

The above example will output:

hello all, I said hi

The two modes of behavior are substantially different. With three arguments, strtr() will replace bytes; with two, it may replace longer substrings.

strtr() behavior comparison

<?php

// Single-byte characters
$singlebyte_string = "baab";
echo strtr($singlebyte_string, "ab", "01"), "\n"; // Byte-by-byte translation

$replace_pairs = ["ab" => "01"];
echo strtr($singlebyte_string, $replace_pairs), "\n"; // Substring translation

// Multi-byte characters
$multibyte_string = "Ä"; // In UTF-8, encoded as two bytes: "\xC3\x84"

$result = strtr($multibyte_string, 'Ä', 'A');
echo bin2hex($result), "\n"; // "4184", where "c3" becomes "41" ("A"), while "84" is kept and breaks UTF-8

$replace_pairs = ['Ä' => 'A'];
echo strtr($multibyte_string, $replace_pairs); // A correct multibyte substring translation

The above example will output:

1001
ba01
4184
A

See Also

• str_replace()
• preg_replace()