php strlen mb_strlen calculates the length of mixed Chinese and English strings

Compare 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. (The encoding method during the test was UTF8)

<?php 
$str=‘中文a字1符‘; 
echo strlen($str); 
echo ‘<br />‘; 
echo mb_strlen($str,‘UTF8‘); 
//输出结果 
//14 
//6 
?>

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
About Chinese and English mixed strings Placeholder calculation:
Using these two functions, you can jointly calculate the placeholder of a mixed Chinese and English string (the placeholder of a Chinese character is 2, and the placeholder of an English character is 1). The calculation method is : If a mixed string has a Chinese character and b English character, the placeholder is:

<?php 
$str=‘中文a字1符‘; 
//计算如下 
echo (strlen($str) + mb_strlen($str,‘UTF8‘)) / 2; 
echo 
//输出结果 
//10 
?>

For example, the strlen($str) value of "Chinese character a 1 character" is 14, mb_strlen($str) The value is 6, then it can be calculated that the placeholder for "Chinese a character 1" is 10.
Attached is an article on the website:
It's still a question about Chinese. 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 is not commented out, otherwise it will be undefined. function problem.

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