# PHP substr_replace() Function

PHP String Reference

## Example

Replace "Hello" with "world":

<?php
echo substr_replace("Hello","world",0);
?>
Run example »

## Definition and Usage

The substr_replace() function replaces a part of a string with another string.

Note: If the start parameter is a negative number and length is less than or equal to start, length becomes 0.

Note: This function is binary-safe.

## Syntax

substr_replace(string,replacement,start,length)

Parameter | Description
--- | ---
string | Required. Specifies the string to check
replacement | Required. Specifies the string to insert

start

Required. Specifies where to start replacing in the string

- A positive number - Start replacing at the specified position in the string
- Negative number - Start replacing at the specified position from the end of the string
- 0 - Start replacing at the first character in the string

length

Optional. Specifies how many characters should be replaced. Default is the same length as the string.

- A positive number - The length of string to be replaced
- A negative number - How many characters should be left at end of string after replacing
- 0 - Insert instead of replace

## Technical Details

Return Value: | Returns the replaced string. If the string is an array then the array is returned
PHP Version: | 4+
Changelog: | As of PHP 4.3.3, all parameters now accept arrays

## More Examples

## Example 1

Start replacing at the 6th position in the string (replace "world" with "earth"):

<?php
echo substr_replace("Hello world","earth",6);
?>
Run example »

## Example 2

Start replacing at the 5th position from the end of the string (replace "world" with "earth"):

<?php
echo substr_replace("Hello world","earth",-5);
?>
Run example »

## Example 3

Insert "Hello" at the beginning of "world":

<?php
echo substr_replace("world","Hello ",0,0);
?>
Run example »

## Example 4

Replace multiple strings at once. Replace "AAA" in each string with "BBB":

<?php
$replace = array("1: AAA","2: AAA","3: AAA");
echo implode("<br>",substr_replace($replace,'BBB',3,3));
?>
Run example »

PHP String Reference

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