Master PHP’s mb_strlen: Handle Multibyte Strings with Ease

In development we often need to handle multibyte strings such as Chinese or Japanese, and standard PHP functions lack proper support. PHP provides the mb_strlen() function to obtain the length of multibyte strings. This article introduces its usage with examples.

The mb_strlen() function is defined in the mbstring extension, so you must ensure the extension is installed and enabled. You can enable it by removing the comment in php.ini or checking with phpinfo().

Syntax of mb_strlen()

int mb_strlen ( string $str [, string $encoding = mb_internal_encoding() ] )

The $str parameter is the multibyte string whose length you want to calculate. The optional $encoding parameter specifies the character encoding; if omitted, it defaults to the value returned by mb_internal_encoding().

Using mb_strlen()

Calculate the length of a Chinese string

<?php
$str = "你好，世界！";
echo mb_strlen($str); // Output: 7
?>

In this example the string contains four Chinese characters and three ASCII characters, so the length is 7.

Specify UTF‑8 encoding

<?php
$str = "こんにちは世界";
echo mb_strlen($str, "UTF-8"); // Output: 6
?>

Here the string has three Japanese characters and three Chinese characters, resulting in a length of 6.

Validate string length against a limit

<?php
$str = "This is a very long sentence.";
$max_length = 20;
if (mb_strlen($str) > $max_length) {
    echo "String is too long.";
} else {
    echo "String is within the limit.";
}
?>

This snippet shows how to enforce a maximum length using mb_strlen().

Overall, mb_strlen() is the PHP function for obtaining the length of multibyte strings. By specifying the encoding, you can flexibly handle strings in different encodings, making length checks and validations more reliable in backend development.