Describe the difference between strlen and mb_strlen in PHP

In PHP, strlen and mb_strlen are functions to find the length of a string, but for some beginners, if they don’t read the manual, they may not be clear about the difference.
The following is an example to explain the difference between the two.

Look at the example first:

Php code

<?php    
//测试时文件的编码方式要是UTF8    
$str=&#39;中文a字1符&#39;;    
echo strlen($str).&#39;<br>&#39;;//14    
echo mb_strlen($str,&#39;utf8&#39;).&#39;<br>&#39;;//6    
echo mb_strlen($str,&#39;gbk&#39;).&#39;<br>&#39;;//8    
echo mb_strlen($str,&#39;gb2312&#39;).&#39;<br>&#39;;//10    
?>

Result analysis: When calculating strlen, a UTF8 Chinese character is treated as 3 lengths, so the length of "Chinese a character 1 character" is 3*4+2=14, When calculating mb_strlen, if the internal code is selected to be UTF8, a Chinese character will be calculated as a length of 1, so the length of "Chinese a character 1 character" is 6.

Using these two functions, you can jointly calculate a What are the placeholders for mixed Chinese and English strings (the placeholder for a Chinese character is 2, and the placeholder for an English character is 1)

Php code

echo (strlen($str) + mb_strlen($str,'UTF8')) / 2;

For example, the strlen($str) value of "Chinese a character 1 character" is 14 , the value of mb_strlen($str) is 6, then it can be calculated that the placeholder of "Chinese a character 1 character" is 10.

Php code

echo mb_internal_encoding();

        PHP’s built-in string length function strlen cannot handle Chinese strings correctly, it only gets the number of bytes occupied by the string. For GB2312 Chinese encoding, the value obtained by strlen is twice the number of Chinese characters, while for UTF-8 encoded Chinese, the difference is three times (under UTF-8 encoding, one Chinese character occupies 3 bytes).

                                Using the mb_strlen function can better solve this problem. The usage of mb_strlen is similar to strlen, except that it has a second optional parameter to specify the character encoding. For example, to get the UTF-8 string $str length, you can use mb_strlen($str,'UTF-8'). If the second parameter is omitted, PHP's internal encoding will be used. The internal encoding can be obtained through the mb_internal_encoding() function.

It should be noted that mb_strlen is not a core function of PHP. Before using it under Windows, you need to make sure that php_mbstring.dll is loaded in php.ini, that is, make sure that the line "extension=php_mbstring.dll" exists and has not been commented out, otherwise There will be an undefined function problem.

This extension needs to be compiled under Linux.