When working with PHP, you may need to find the first character position of a substring. This guide explains the operation, shows what its arguments mean, and uses three separate examples to make the result easier to understand.
mb_strpos: The returned index counts characters, unlike byte-oriented strpos().
What Is mb_strpos in PHP?
Find the first character position of a substring. The returned index counts characters, unlike byte-oriented strpos().
Syntax:
mb_strpos(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: Always check against false with a strict comparison because zero is a valid position.
Example 1: Basic Usage
This example introduces the operation with a short and predictable input.
<?php
var_dump(mb_strpos("Café menu", "menu", 0, "UTF-8"));
The code focuses on the main operation. The returned index counts characters, unlike byte-oriented strpos().
Example 2: Another Case
Now compare a different input, locale, date, or option to see another part of the behavior.
<?php
var_dump(mb_strpos("hello", "xyz", 0, "UTF-8"));
What changes? Always check against false with a strict comparison because zero is a valid position.
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
$messages = ["Bonjour à tous", "Hello team"];
foreach ($messages as $message) {
if (mb_strpos($message, "team", 0, "UTF-8") !== false) {
echo $message . PHP_EOL;
}
}
The practical example demonstrates how to apply this operation to multiple values, a reusable task, or a validated input. The returned index counts characters, unlike byte-oriented strpos().
Important Behavior and Edge Cases
- Core behavior: The returned index counts characters, unlike byte-oriented strpos().
- Inputs and results: Always check against false with a strict comparison because zero is a valid position.
- Alternatives: mb_stripos() ignores case; mb_strrpos() finds the last occurrence.
- Compatibility: mbstring is required for mb_* functions.
Comparison With Related Functions
| Function or Approach | When to Use It |
|---|---|
mb_strpos | Find the first character position of a substring. |
| Related PHP approach | mb_stripos() ignores case; mb_strrpos() finds the last occurrence. |
Common Beginner Mistakes
| Mistake | Correct Approach |
|---|---|
| Using an incorrect input or option | Always check against false with a strict comparison because zero is a valid position. |
| Confusing this API with a related operation | mb_stripos() ignores case; mb_strrpos() finds the last occurrence. |
| Assuming output is identical across environments | Check return values and required extensions or versions. mbstring is required for mb_* functions. |
Key Takeaways
- mb_strpos helps you find the first character position of a substring.
- The returned index counts characters, unlike byte-oriented strpos().
- Always check against false with a strict comparison because zero is a valid position.
Use mb_strpos when you need to find the first character position of a substring. 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.