Using PHP mb_strlen to Handle Multibyte Strings

In PHP, handling multibyte characters is a common issue because languages such as Chinese use UTF-8 encoding, and traditional string length functions may give inaccurate results. PHP provides the convenient mb_strlen function to obtain the length of multibyte strings.

Before using mb_strlen , ensure that the mbstring extension is installed and enabled. In the php.ini file you should find the line:

;extension=mbstring

If the line starts with a semicolon, it is commented out; remove the semicolon and restart your web server or PHP interpreter.

The following simple example demonstrates how to use mb_strlen to calculate the length of a multibyte string.

<?php
$str = "你好，世界！";
$length = mb_strlen($str, "UTF-8");

echo "字符串 " . $str . " 的长度是： " . $length;
?>

This code defines a variable $str containing a multibyte string, calls mb_strlen with the UTF-8 encoding to compute its length, stores the result in $length , and prints the length using echo .

When the script is executed, the output will be:

字符串 "你好，世界！" 的长度是：6

The second argument "UTF-8" is specified because the string uses UTF-8 encoding; other encodings should be set accordingly.

Besides calculating length, mb_strlen can also be used to check whether a multibyte string is empty. If a string contains only whitespace or invisible characters, it is still considered non-empty.

To handle such cases, combine trim with mb_strlen to remove surrounding whitespace before checking the length.

<?php
$str = "    ";
$trimmedStr = trim($str);
if (mb_strlen($trimmedStr, "UTF-8") > 0) {
    echo "字符串不为空";
} else {
    echo "字符串为空";
}
?>

In this example, $str holds a multibyte string consisting only of spaces. After trimming, mb_strlen determines whether the resulting string has a length greater than zero and outputs the appropriate message.

These examples illustrate the powerful capabilities of mb_strlen for handling multibyte strings, providing accurate length calculations and enabling robust empty-string checks, which are essential when developing websites or processing multilingual data.