strtoupper
substr_compare
String Functions
PHP Manual

# strtr

Translate characters or replace substrings

### Description

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 The return value is a string where all the occurrences of the array keys have been replaced by the corresponding values.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; additionaly, 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.

### Parameters

`str`

  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', ...).

### 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.

### Examples

Example #1 strtr example

`<?php
//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

`<?php
$trans = array("h" => "-", "hello" => "hi", "hi" => "hello");
echo 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

`<?php
echo strtr("baab", "ab", "01"),"\n";
$trans = array("ab" => "01");
echo strtr("baab", $trans);
?>`

The above example will output:

    1001
    ba01

### See Also

- str_replace
- preg_replace