PHP String substr_replace() Function

The substr_replace is an in-built function of PHP, which replaces a part of the string with another text within a string. PHP 4+ versions support this function. The index in the original string is passed as a parameter to which the replacement is to be performed. An array of string can also be passed as a parameter to this function, and in that case, a replacement will be done for each string at every turn (See Example 5).

Note: The substr_replace() is a binary-safe function.

Syntax

The syntax for the substr_replace() is given below, which accepts four arguments.

Parameters

The substr_replace() consists of four parameters, in which three parameters are mandatory to pass in this function whereas $length parameter is optional. All these parameters are discussed below in detail:

$string (required) - It is the main string parameter of this function, which specifies the input string in which the replacement will be done. This is a mandatory parameter.

$replacement (required) - It is a mandatory parameter of the substr_replace(), which specifies the string to insert. The $replacement contains the string to which the replacement is going to be done.

$start (required) - It is also a mandatory parameter, which specifies the position from where the replacement needs to be started. This parameter holds the integer value. There are three conditions for this parameter:

• If the value passed in $start is a positive number, then the replacement starts from the specified position in the string.
• If the $start has a negative value, then the replacement starts from the specified position at the end of the string.
• If the $start is 0, then the replacement will start from the first character of the string.

$length (optional) - It is an optional parameter of this function, which specifies how many characters, are to be replaced in the string. In case $length parameter is not passed in substr_replace(), then replacement stops at the end of the string. There are also three conditions for this parameter:

• If the $length value is positive, then given length of the string will be replaced with the new string.
• If the $length is negative, then the number of character should be left at the end after replacing the string.
• If the $length is 0, then insertion is done instead of replacement.

Return Values

The substr_raplace() returns a string after the replacement is done. In case, if the string is an array, then it returns an array.

ChangeLog

From PHP 4.3.3, all the parameters accept arrays.

Examples

There are a few numbers of examples given, by which we can learn the practical implementation of the substr_replace() function.

Example 1

Output:

In the above example, replacement is started from 6th position. "earth" is replaced with "javatpoint".

Hello javatpoint

Example 2

Output:

In the above example, replacement is started from 6th position in the first case. In the second case, a negative value is passed, so replacement is done at the end from 10th position in the string.

Hello PHP
Hello PHP

Example 3

Output:

In the above example, we have used the fourth $length parameter, whose value is passed 0. Hence the insertion of string "Hello" is done rather than replacement.

Hello PHP!

Example 4

Output:

Welcome to javatpoint

Example 5: Replacement multiple strings at once

Output:

X: BBBB; Y: BBBB; Z: BBBB
X: XXXX; Y: YYYY; Z: ZZZZ
X: XXXXAA; Y: YYYYA; Z: ZZZZ

Note: Implode() function is used here for the array to string conversion.