Mastering PHP’s strlen(): How to Accurately Measure String Length

strlen() is a commonly used PHP string function that calculates the length of a string, including spaces and special characters but excluding the null character.

The syntax is: int strlen ( string $string ) $string represents the string whose length is to be calculated.

Example 1: Calculate string length

$str = "Hello, world!"; // define a string
echo strlen($str); // output string length

The output is:

13

Example 2: Calculate length ignoring spaces

$str = "   Hello,   world!    "; // string with spaces
echo strlen($str); // length with spaces
echo strlen(trim($str)); // length after trimming spaces

The output is:

23
13

These examples show that strlen() is widely used for quickly counting string length, useful in scenarios such as limiting usernames on social sites or product name lengths in e‑commerce.

Note that strlen() only reliably handles UTF‑8 and ISO‑8859‑1 encoded strings; other encodings may produce incorrect results.

When using strlen(), be aware of special or Chinese characters, as their byte size varies with encoding and can affect the length calculation.