PHP str_replace

Summary: in this tutorial, you’ll learn how to use the PHP str_replace() function to replace all occurrences of a substring with a new string

Introduction to the PHP str_replace() function #

The PHP str_replace() function returns a new string with all occurrences of a substring replaced with another string.

The following shows the syntax of the str_replace() function:

str_replace ( 
    array|string $search , 
    array|string $replace , 
    string|array $subject , 
    int &$count = null 
) : string|arrayCode language: PHP (php)

The str_replace() has the following parameters:

• The $search is a substring to be replaced.
• The $replace is the replacement string that replaces the$search value.
• The $subject is the input string
• The $count returns the number of replacements that the function performed. The $count is optional.

If the $search and $replace arguments are arrays, the str_replace() takes each value from the $search array (from left to right) and replaces it with each value from the $replace array.

If the $replace array has fewer elements than the $search array, the str_replace() function uses an empty string for the replacement values.

If the $search is an array and the $replace is a string, then the str_replace() function replaces every element in the $search with the $replace string.

Note that the str_replace() doesn’t change the input string ($subject). It returns a new array with the $search replaced with the $replace.

PHP str_replace() function examples #

Let’s take some examples of using the PHP str_replace() function.

Simple PHP str_replace() function examples #

The following example uses the str_replace() function to replace the string 'Hello' with 'Hi' in the string 'Hello there':

<?php

$str = 'Hello there';
$new_str = str_replace('Hello', 'Hi', $str);

echo $new_str . '<br>'; // Hi there

echo $str . '<br>'; // Hello thereCode language: PHP (php)

Try it

Output:

Hi there
Hello thereCode language: PHP (php)

As shown in the output, the str_replace() doesn’t change the input string but returns a new string with the substring 'Hello' replaced by the string 'Hi';

The following example uses the str_replace() function to replace the substring 'bye' with the string 'hey' in the string 'bye bye bye':

<?php

$str = 'bye bye bye';
$new_str = str_replace('bye', 'hey', $str);

echo $new_str; // hey hey heyCode language: PHP (php)

Try it

Output:

hey hey heyCode language: PHP (php)

Using PHP str_replace() function with the count argument example #

The following example uses the str_replace() function with the count argument:

<?php 

$str = 'Hi, hi, hi';
$new_str = str_replace('hi', 'bye', $str, $count);

echo $count; // 2Code language: PHP (php)

Try it

In this example, the str_replace() function replaces the substring 'hi' with the string 'bye' in the string 'Hi, hi, hi'.

The count returns two because the str_replace() function only replaces the substring 'hi' not 'Hi'.

PHP str_replace() function with multiple replacements example #

The following example uses the str_replace() function to replace the fox with wolf and dog with cat in the string 'The quick brown fox jumps over the lazy dog':

<?php

$str = 'The quick brown fox jumps over the lazy dog';
$animals = ['fox', 'dog'];
$new_animals = ['wolf', 'cat'];

$new_str = str_replace($animals, $new_animals, $str);

echo $new_str;Code language: PHP (php)

Try it

Output:

The quick brown wolf jumps over the lazy catCode language: PHP (php)

Since the str_replace() function replaces left to right, it might replace previously replaced value while doing multiple replacements. For example:

<?php

$str = 'apple';

$fruits = ['apple', 'orange', 'banana'];
$replacements = ['orange', 'banana', 'strawberry'];

$new_str = str_replace($fruits, $replacements, $str, $count);

echo $new_str; // strawberry
echo $count; // 3Code language: PHP (php)

Try it

In this example, the string apple is replaced with orange, orange is replaced with banana, and banana is replaced with strawberry. The returned string is strawberry.

PHP str_ireplace() function #

To search for a string case-insensitively and replace it with a replacement string, you use the str_ireplace() function. For example:

<?php

$str = 'Hi, hi, hi';
$new_str = str_ireplace('hi', 'bye', $str, $count);

echo $new_str; // bye, bye, byeCode language: PHP (php)

Try it

In this example, the str_ireplace() function replaces the substring 'hi' or 'Hi' with the string 'bye'.

Summary #

• Use the str_replace() function to replace a substring with another string.
• Use the str_ireplace() function to search a substring case-insensitively and replace it with another string.