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PHP str_replace()

Reading time 2 min
Published Aug 14, 2017
Updated Sep 24, 2019

PHP str_replace: Main Tips

  • By using this function, you can replace characters in a text string.
  • PHP str_replace is case-sensitive. If you need to perform a case-insensitive search, try str_ireplace() function.
  • If the variable specified by the third argument is an array, the function will check every array element and will return an array.
  • If the first and second function arguments are both arrays, and the second argument has fewer elements than the first, an empty string will be used as a replacement.
  • If the first argument is an array and the second is a string, the string will be used for every array element.

Function Explained

By using the str_replace PHP function, you will replace a string specified in the first argument with a string specified in the second argument. The third argument is a string or an array in which search and replacement will take place. PHP str_replace returns a string or an array with the replaced values.

Let's see a simple example:

Example
<?php
  echo str_replace("world","Peter","Hello world!"); 
?>
Theory is great, but we recommend digging deeper!

Correct Syntax

Here we have is a simple scheme for the correct syntax of the PHP string replace function:

str_replace(find, replace, string, count)

In the table below, each parameter of the function is described separately for you to get a better idea:

Parameter Description
find Necessary. Defines the value that has to be found.
replace Necessary. Defines the replacement value.
string Necessary. Specifies a string where the search will take place.
count Not necessary. Sets a variable that counts the changes made.

Code Examples

In the example you can see below, PHP string replace function finds the word cat in the $arr array and replaces it with the word lama. We only have one change done in this case, but the function would successfully replace all the words cat if the code would consist of more than one.

Variable $i holds a value of how many replacements did the function do:

Example
<?php
  $arr = array("Best", "pet", "is", "cat");
  print_r(str_replace("cat", "lama", $arr, $i));
  echo "Replace count: $i"; 
?>

In the example below, PHP str_replace function replaces two strings in the $arr array with the letter B. See for yourself:

Example
<?php
  $find = array("Hello", "world");
  $replace = "B";
  $arr = array("Hello", "world", "!");
  print_r(str_replace($find, $replace, $arr));
?>