When working with PHP, you may need to convert a Unicode string to lowercase. This guide explains the operation, shows what its arguments mean, and uses three separate examples to make the result easier to understand.
mb_strtolower: This applies Unicode lowercase mappings and supports characters beyond ASCII.
What Is mb_strtolower in PHP?
Convert a Unicode string to lowercase. This applies Unicode lowercase mappings and supports characters beyond ASCII.
Syntax:
mb_strtolower(string $string, ?string $encoding = null): string
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: Lowercasing alone is not full Unicode normalization or locale-aware comparison.
Example 1: Basic Usage
This example introduces the operation with a short and predictable input.
<?php
echo mb_strtolower("CAFÉ", "UTF-8");
The code focuses on the main operation. This applies Unicode lowercase mappings and supports characters beyond ASCII.
Example 2: Another Case
Now compare a different input, locale, date, or option to see another part of the behavior.
<?php
echo mb_strtolower("HELLO WORLD", "UTF-8");
What changes? Lowercasing alone is not full Unicode normalization or locale-aware comparison.
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
$tags = ["PHP", "Résumé", "NEWS"];
foreach ($tags as $tag) {
echo mb_strtolower($tag, "UTF-8") . PHP_EOL;
}
The practical example demonstrates how to apply this operation to multiple values, a reusable task, or a validated input. This applies Unicode lowercase mappings and supports characters beyond ASCII.
Important Behavior and Edge Cases
- Core behavior: This applies Unicode lowercase mappings and supports characters beyond ASCII.
- Inputs and results: Lowercasing alone is not full Unicode normalization or locale-aware comparison.
- Alternatives: mb_convert_case() offers additional case-conversion modes.
- Compatibility: mbstring is required for mb_* functions.
Comparison With Related Functions
| Function or Approach | When to Use It |
|---|---|
mb_strtolower | Convert a unicode string to lowercase. |
| Related PHP approach | mb_convert_case() offers additional case-conversion modes. |
Common Beginner Mistakes
| Mistake | Correct Approach |
|---|---|
| Using an incorrect input or option | Lowercasing alone is not full Unicode normalization or locale-aware comparison. |
| Confusing this API with a related operation | mb_convert_case() offers additional case-conversion modes. |
| Assuming output is identical across environments | Check return values and required extensions or versions. mbstring is required for mb_* functions. |
Key Takeaways
- mb_strtolower helps you convert a Unicode string to lowercase.
- This applies Unicode lowercase mappings and supports characters beyond ASCII.
- Lowercasing alone is not full Unicode normalization or locale-aware comparison.
Use mb_strtolower when you need to convert a Unicode string to lowercase. 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.