Do you know the difference between strlen and mb_strlen in php?

Commonly used functions in php to calculate string length are: strlen and mb_strlen. When the characters are all English characters, the two are 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.

strlen() function returns the length of the string. If successful, it returns the length of the string. If the string is If empty, 0 is returned.

mb_strlen - Get the length of the string,

Syntax

mb_strlen ($str, $encoding)

str The string to check the length.

encoding The parameter is character encoding. If omitted, the internal character encoding is used.

Return value

Returns the number of characters contained in the string str with encoding encoding. Multibyte characters are counted as 1.

Returns FALSE if the given encoding is invalid.

The following is an example of the difference between the two.

Look at the example first:

<?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 as 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 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, "Chinese a character 1 The strlen($str) value of "character" is 14, and the value of mb_strlen($str) is 6. It can be calculated that the placeholder of "Chinese a character 1 character" is 10.

echo mb_internal_encoding();

PHP built-in string The 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, you need to make sure that php_mbstring.dll is loaded in php.ini, that is, make sure that "extension=php_mbstring.dll" A line exists and is not commented, otherwise an undefined function problem will occur.

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