PHP str_ireplace() Function: Usage and Examples

When you need to replace literal text without ASCII case sensitivity, it helps to understand both the normal result and what changes with different inputs. This guide focuses on practical examples rather than repeating PHP background material.

str_ireplace provides the behavior described below. The fourth argument receives the number of replacements by reference. Multiple search strings are applied sequentially.

What Is str_ireplace in PHP?

Replace literal text without ascii case sensitivity. The fourth argument receives the number of replacements by reference. Multiple search strings are applied sequentially.

Its syntax is:

str_ireplace(array|string $search, array|string $replace, array|string $subject, &$count = ...): array|string

Parameters and return value: Read the argument names and optional values in the signature above. Methods use an existing object, while stand-alone functions take direct arguments. The examples demonstrate the relevant arguments and the value returned or the object modified.

Important: Matching is not full Unicode case folding, and array replacements may interact.

Example 1: Basic Usage

This first example demonstrates how to replace literal text without ASCII case sensitivity with a small input.

<?php

$text = "ERROR: error detected";
echo str_ireplace("error", "warning", $text);

Output:

warning: warning detected

The example uses the simplest useful form. The fourth argument receives the number of replacements by reference. Multiple search strings are applied sequentially. The output may depend on the active ICU locale, PHP configuration, or input supplied to the function.

Example 2: Another Case

Here the input or option changes, making it easier to see where the behavior differs. Matching is not full Unicode case folding, and array replacements may interact.

<?php

$changes = 0;
echo str_ireplace("offline", "online", "OFFLINE / offline", $changes);
echo " Changes: " . $changes;

Output:

online / online Changes: 2

Compare the result to the first example. str_replace() is case-sensitive; preg_replace() uses regular expressions.

Practical Example: Applying the Function

This standalone example shows how the same operation fits into a small application task.

<?php

$statusMessages = ["Error loading", "WARNING", "error writing"];
$cleanMessages = str_ireplace("error", "issue", $statusMessages);
print_r($cleanMessages);

Output:

Array
(
    [0] => issue loading
    [1] => WARNING
    [2] => issue writing
)

The example keeps the operation visible and gives you a starting point for using it in an application. Matching is not full Unicode case folding, and array replacements may interact.

Important Behavior and Edge Cases

• Core behavior: The fourth argument receives the number of replacements by reference. Multiple search strings are applied sequentially.
• Return value: Check the result separately from changes to passed-in arrays, iterators, or object state.
• Data constraints: Matching is not full Unicode case folding, and array replacements may interact.
• Environment: Run this example under a PHP version supporting the API; check results and exceptions before using them.

Comparison With Related Functions

Common Beginner Mistakes

Key Takeaways

• str_ireplace helps you replace literal text without ASCII case sensitivity.
• The fourth argument receives the number of replacements by reference. Multiple search strings are applied sequentially.
• Matching is not full Unicode case folding, and array replacements may interact.
• str_replace() is case-sensitive; preg_replace() uses regular expressions.

str_ireplace is useful when you need to replace literal text without ASCII case sensitivity. Start with the small examples, then adapt the practical example while respecting its input and environment requirements.