String Functions
PHP Manual


(PHP 4, PHP 5, PHP 7)

strtrTranslate characters or replace substrings


string strtr ( string $str , string $from , string $to )
string strtr ( string $str , array $replace_pairs )

If given three arguments, this function returns a copy of str 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 str 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 The return value is a string where all the occurrences of the array keys have been replaced by the corresponding values.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 str. However, this function will be the most efficient when all the keys have the same size.



The string being translated.


The string being translated to to.


The string replacing from.


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', ...).

Return Values

Returns the translated string.

If replace_pairs contains a key which is an empty string (""), FALSE will be returned. If the str is not a scalar then it is not typecasted into a string, instead a warning is raised and NULL is returned.


Example #1 strtr() example

//In this form, strtr() does byte-by-byte translation
//Therefore, we are assuming a single-byte encoding here:
$addr strtr($addr"äåö""aao");

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.

Example #2 strtr() example with two arguments

= array("h" => "-""hello" => "hi""hi" => "hello");
strtr("hi all, I said hello"$trans);

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.

Example #3 strtr() behavior comparison

echo strtr("baab""ab""01"),"\n";

$trans = array("ab" => "01");

The above example will output:


See Also

String Functions
PHP Manual