Example introduction to the difference between string length functions strlen and mb_strlen, strlenmb_strlen_PHP tutorial

Example introduction to the difference between string length functions strlen and mb_strlen, strlenmb_strlen

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, they may not be clear about the difference without reading the manual.
The difference between the two is explained below through examples.

Look at the example first:

<&#63;php 
//测试时文件的编码方式要是UTF8 
$str='中文a字1符'; 
echo strlen($str).'<br>';//14 
echo mb_strlen($str,'utf8').'<br>';//6 
echo mb_strlen($str,'gbk').'<br>';//8 
echo mb_strlen($str,'gb2312').'<br>';//10 
&#63;>

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, the selected internal code is 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, the strlen($str) value of "Chinese a character 1 character" is 14, and the mb_strlen($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 length of the UTF-8 string $str, you can use mb_strlen($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 it will An undefined function problem occurred.

The strlen function measures the string length including the end identifier

The strlen function does not include the length of '\0'. The result of sizeof calculation only includes the length of '\0':
char str[] = "This is a test string two";
cout< ;<"str sizeof is :"<cout<<"str strlen is :"<
output:
str sizeof is:26
str strlen is:25

Look at the above example to make it clearer!

What are the functions of strlen() and mb_strlen

In PHP, strlen and mb_strlen are functions to find the length of a string, but for some beginners, they may not be clear about the difference without reading the manual.
The following uses examples to explain the difference between the two.
Look at the example first:
';/ /14 echo mb_strlen($str,'utf8').'
';//6 echo mb_strlen($str,'gbk').'
';//8 echo mb_strlen($str, 'gb2312').'
';//10 ?>

Result analysis: When calculating strlen, a UTF8 Chinese character is treated as 3 characters in length, so "Chinese a character is 1 character "The length 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, the strlen($str) value of "Chinese a character 1 character" is 14, and the mb_strlen($str) value is 6, then you can It is calculated that the placeholder for "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 gets Just 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 length of the UTF-8 string $str, you can use mb_strlen($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 it will An undefined function problem occurred.

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