The difference between strlen and mb_strlen in PHP

Common functions for calculating string length in php are: strlen and mb_strlen. When the characters are all English characters, the two are the same. Here we mainly compare the two calculation results when Chinese and English are mixed.

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 uses examples to explain the difference between the two.

Look at the example first:

<?php  
//测试时文件的编码方式为gbk
$str=&#39;中文a字1符&#39;;  
echo strlen($str).&#39;<br>&#39;;//10 
echo mb_strlen($str,&#39;utf8&#39;).&#39;<br>&#39;;//7  
echo mb_strlen($str,&#39;gbk&#39;).&#39;<br>&#39;;//6  
echo mb_strlen($str,&#39;gb2312&#39;).&#39;<br>&#39;;//6 
echo mb_strlen($str).&#39;<br>&#39;;//10
?>

Result analysis:

When calculating strlen, the Chinese character of a gbk is 2 lengths, so "Chinese a character 1 character" The length is 2*4 2=10. When calculating mb_strlen, when the internal code is gbk, a Chinese character will be treated as a character length.

Using these two functions, you can jointly calculate the occupancy of a mixed Chinese and English string (the occupancy of a Chinese character is 2, and the occupancy of an English character is 1)

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

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

echo mb_internal_encoding();

PHP's built-in string length function strlen cannot correctly handle Chinese strings. 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, 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 the problem of undefined function will occur.

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