Translate characters or replace substrings

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- PHP Manual
- String Functions
- Translate characters or replace substrings

# strtr

(PHP 4, PHP 5, PHP 7, PHP 8)

strtr — Translate characters or replace substrings

### Description

strtr(string `$string`, string `$from`, string `$to`): string

Alternative signature (not supported with named arguments):

strtr(string `$string`, array `$replace_pairs`): string

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 The return value is a string where all the occurrences of the array keys have been replaced by the corresponding values.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

Example #1 strtr() example

    <?php
    $addr = "The river å";

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

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() - Replace all occurrences of the search string with the replacement string
- preg_replace() - Perform a regular expression search and replace