Understanding PHP strlen() Function: Syntax, Examples, and Usage

strlen() is a commonly used PHP string function that returns the length of a string, counting spaces and special characters but excluding the terminating null byte.

Syntax of strlen()

<code>int strlen ( string $string )</code>

Here, $string represents the string whose length is to be measured.

Code Examples

Example 1: Calculate string length

<code>$str = "Hello, world!"; // define a string
echo strlen($str); // output the length of the string</code>

The output is:

<code>13</code>

Example 2: Length ignoring surrounding spaces

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

The output is:

<code>23
13</code>

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

Note that strlen() works correctly with UTF‑8 and ISO‑8859‑1 encoded strings; other encodings may produce inaccurate results.

When using strlen() , be aware that special characters or Chinese characters may occupy multiple bytes depending on the encoding, affecting the length calculation.

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