How to Use PHP strlen() to Measure String Length – Syntax, Examples, and Tips

In PHP development, obtaining the length of a string is a common requirement, and the built‑in strlen() function is used for this purpose.

1. Getting the length of a string

int strlen ( string $string )

The function accepts a single string argument and returns its length in bytes.

$foo = "Hello, World!";
$length = strlen($foo);
echo "String length is: " . $length; // Output: String length is: 13

2. Checking if a string is empty

$bar = "";
if (strlen($bar) == 0) {
    echo "String is empty";
} else {
    echo "String is not empty";
}

3. Validating that a string does not exceed a certain length

$password = "abcd";
$length = strlen($password);
if ($length > 8) {
    echo "Password is too long, please re‑enter";
} else {
    echo "Password length is acceptable";
}

4. Getting the length of a multibyte (e.g., Chinese) string

$chinese = "你好，世界！";
$length = strlen($chinese);
echo "String length is: " . $length; // Output may be 15 because each Chinese character occupies multiple bytes

Note that strlen() counts bytes, not characters; for multibyte strings you should use mb_strlen() to obtain the actual character count.

Measuring string length is frequently used for input validation, string manipulation, and conditional logic. By mastering strlen() , developers can efficiently handle these tasks in PHP.