PHP strlen() Function: Usage and Examples

PHP strlen() counts the bytes in a PHP string, not Unicode characters. The examples below show how the call behaves, where it is useful, and which limitations matter.

What Is strlen() in PHP?

Counts the bytes in a PHP string, not Unicode characters.

Its call structure is:

strlen($string)

The arguments identify the values or resources passed to strlen(). Read the examples with attention to the type of each supplied argument and to whether the function modifies its input or returns a separate result.

Example 1: Basic Usage

This example introduces strlen with a direct call and a small, readable input.

<?php

echo strlen("hello");

Output:

5

Counts the bytes in a PHP string, not Unicode characters. For UTF-8 text, use mb_strlen() to count code points or grapheme_strlen() for visible graphemes.

Example 2: Another Behavior or Input

Compare this input with the previous example: changing the data or option can affect how strlen behaves.

<?php

echo strlen("é"); // UTF-8 uses more than one byte.

Output:

2

The changed input illustrates why output may differ with the chosen values or environment. For UTF-8 text, use mb_strlen() to count code points or grapheme_strlen() for visible graphemes.

Practical Example: Using the Feature

The following example incorporates strlen into a workflow. Values such as paths, connection handles and configuration options must come from trusted application settings.

<?php

$payload = "ABC123"; if (strlen($payload) <= 16) { echo "Within byte limit"; }

Output:

Within byte limit

In a real application, check each operation result, validate values before use and clean up acquired resources. For UTF-8 text, use mb_strlen() to count code points or grapheme_strlen() for visible graphemes.

Important Behavior and Edge Cases

• Purpose: Counts the bytes in a PHP string, not Unicode characters.
• Key limitation: For UTF-8 text, use mb_strlen() to count code points or grapheme_strlen() for visible graphemes.
• Failure handling: Check return values and handle invalid inputs and unavailable operating-system or extension features where relevant.

Comparison With Related Functions

Common Beginner Mistakes

Key Takeaways

• Counts the bytes in a PHP string, not Unicode characters.
• For UTF-8 text, use mb_strlen() to count code points or grapheme_strlen() for visible graphemes.
• Use the examples as starting points, and adapt environmental paths, resources and permissions rather than assuming fixed results.

strlen is useful when its specific behavior fits the problem. The safest implementations combine the correct API with input validation, error checking and resource cleanup.