# ereg_replace

(PHP 4, PHP 5)

ereg_replace — Replace regular expression

### Description

string ereg_replace ( string `$pattern` , string `$replacement` , string `$string` )

This function scans `string` for matches to `pattern` , then replaces the matched text with `replacement` .

### Parameters

`pattern`

  A POSIX extended regular expression.

`replacement`

  If `pattern` contains parenthesized substrings, `replacement` may contain substrings of the form \\digit, which will be replaced by the text matching the digit'th parenthesized substring; \\0 will produce the entire contents of string. Up to nine substrings may be used. Parentheses may be nested, in which case they are counted by the opening parenthesis.

`string`

  The input string.

### Return Values

The modified string is returned. If no matches are found in `string` , then it will be returned unchanged.

### Examples

For example, the following code snippet prints "This was a test" three times:

Example#1 ereg_replace() example

`<?php
$string = "This is a test";
echo str_replace(" is", " was", $string);
echo ereg_replace("( )is", "\\1was", $string);
echo ereg_replace("(( )is)", "\\2was", $string);
?>`

One thing to take note of is that if you use an integer value as the `replacement` parameter, you may not get the results you expect. This is because ereg_replace() will interpret the number as the ordinal value of a character, and apply that. For instance:

Example#2 ereg_replace() example

`<?php
/* This will not work as expected. */
$num = 4;
$string = "This string has four words.";
$string = ereg_replace('four', $num, $string);
echo $string; /* Output: 'This string has words.' */
/* This will work. */
$num = '4';
$string = "This string has four words.";
$string = ereg_replace('four', $num, $string);
echo $string; /* Output: 'This string has 4 words.' */
?>`

Example#3 Replace URLs with links

`<?php
$text = ereg_replace("[[:alpha:]]+://[^<>[:space:]]+[[:alnum:]/]",
"<a href=\"\\0\">\\0</a>", $text);
?>`

### Notes

Tip

preg_replace(), which uses a Perl-compatible regular expression syntax, is often a faster alternative to ereg_replace().

### See Also

- ereg()
- eregi()
- eregi_replace()
- str_replace()
- preg_match()