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

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

Syntax of the strlen() function:

int strlen ( string $string )

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

Concrete code examples:

Example 1: Calculating the length of a string

$str = "Hello, world!"; //定义一个字符串
 echo strlen($str); //输出字符串的长度

The output is:

13

Example 2: Calculating string length while ignoring spaces

$str = "   Hello,   world!    "; //定义一个带有空格的字符串
 echo strlen($str); //输出字符串的长度
 echo strlen(trim($str)); //输出去除空格后字符串的长度

The output is:

23
13

From the above examples, it can be seen that the strlen() function is widely used for string handling. It can quickly count a string's length, suitable not only for general string processing tasks but also for scenarios such as limiting user nickname lengths on social sites or product name lengths in e‑commerce.

Note that the strlen() function only supports UTF‑8 and ISO‑8859‑1 encoded strings; using other encodings may lead to incorrect length calculations.

When using strlen(), be aware that special characters or Chinese characters may occupy different numbers of bytes under various encodings, affecting the length result.

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