PHP mb_strripos() Function: Usage and Examples

When working with PHP, you may need to find the last case-insensitive character position. This guide explains the operation, shows what its arguments mean, and uses three separate examples to make the result easier to understand.

mb_strripos: Searches backward and returns a zero-based character position or false.

What Is mb_strripos in PHP?

Find the last case-insensitive character position. Searches backward and returns a zero-based character position or false.

Syntax:

mb_strripos(string $haystack, string $needle, int $offset = 0, ?string $encoding = null): int|false

Parameters and return value: The signature above identifies the arguments and return type where the API has a single call. For topic guides, follow the sequence of calls in the examples. Always distinguish a returned value from an object or variable modified by reference.

Important: Use strict false comparison. Case folding does not guarantee locale-specific matching rules.

Example 1: Basic Usage

This example introduces the operation with a short and predictable input.

<?php

var_dump(mb_strripos("A.txt and B.TXT", ".txt", 0, "UTF-8"));

The code focuses on the main operation. Searches backward and returns a zero-based character position or false.

Example 2: Another Case

Now compare a different input, locale, date, or option to see another part of the behavior.

<?php

var_dump(mb_strripos("one two one", "ONE", 0, "UTF-8"));

What changes? Use strict false comparison. Case folding does not guarantee locale-specific matching rules.

Practical Example: Applying It in an Application

Use the following separate example as a starting point for a small application task. Check any extension or environment requirements below before running it.

<?php

$paths = ["archive.TXT", "notes.txt", "report.csv"];
foreach ($paths as $path) {
    $position = mb_strripos($path, ".txt", 0, "UTF-8");
    if ($position !== false && $position === mb_strlen($path, "UTF-8") - 4) {
        echo $path . PHP_EOL;
    }
}

The practical example demonstrates how to apply this operation to multiple values, a reusable task, or a validated input. Searches backward and returns a zero-based character position or false.

Important Behavior and Edge Cases

• Core behavior: Searches backward and returns a zero-based character position or false.
• Inputs and results: Use strict false comparison. Case folding does not guarantee locale-specific matching rules.
• Alternatives: mb_stripos() finds the first case-insensitive occurrence.
• Compatibility: mbstring is required for mb_* functions.

Comparison With Related Functions

Common Beginner Mistakes

Key Takeaways

• mb_strripos helps you find the last case-insensitive character position.
• Searches backward and returns a zero-based character position or false.
• Use strict false comparison. Case folding does not guarantee locale-specific matching rules.

Use mb_strripos when you need to find the last case-insensitive character position. Start with the first example, compare the second, and adapt the practical example to your inputs. Confirm the return value and environment requirements before adding it to production code.