Case-Insensitive String Replacement in PHP

This article explains how to perform case-insensitive string replacement in PHP using the built-in str_ireplace() function. You will learn the basic syntax of the function, how it differs from str_replace(), and see practical examples of how to replace single words as well as multiple values using arrays.

The str_ireplace() function is the case-insensitive version of str_replace(). It searches a subject string for a specific value and replaces it with a new value, ignoring whether the characters are uppercase or lowercase.

Syntax of str_ireplace()

The function accepts four parameters:

str_ireplace(mixed $search, mixed $replace, mixed $subject, int &$count = null): mixed

• $search: The value being searched for (can be a string or an array).
• $replace: The replacement value (can be a string or an array).
• $subject: The string or array being searched and replaced on.
• $count (Optional): A variable that will be filled with the number of matched and replaced needles.

Basic Example

In this example, the word “apple” is searched in a case-insensitive manner and replaced with “orange”.

$text = "I love eating Apple pie and APPLES.";
$new_text = str_ireplace("apple", "orange", $text);

echo $new_text; 
// Output: I love eating orange pie and oranges.

As demonstrated, both “Apple” (capitalized) and “APPLES” (uppercase) are successfully matched and replaced.

Using Arrays with str_ireplace()

You can pass arrays to both the search and replacement parameters to perform multiple replacements at once.

$search_words = ["BROWN", "FOX", "LAZY"];
$replacements = ["white", "cat", "playful"];
$phrase = "The quick Brown Fox jumps over the lazy dog.";

$new_phrase = str_ireplace($search_words, $replacements, $phrase);

echo $new_phrase;
// Output: The quick white cat jumps over the playful dog.

Tracking the Number of Replacements

If you need to know how many replacements were made during the operation, pass a variable as the fourth argument.

$text = "Go green, think Green, live green.";
$new_text = str_ireplace("green", "blue", $text, $count);

echo $new_text; // Output: Go blue, think blue, live blue.
echo "Replacements made: " . $count; // Output: Replacements made: 3