Differences between strlen and mb_strlen functions in PHP

In PHP, strlen and mb_strlen are functions used to evaluate the string length. However, for some beginners, if they do not read the manual, they may not know the difference.

In PHP, strlen and mb_strlen are functions used to evaluate the string length. However, for some beginners, if they do not read the manual, they may not know the difference.

There are two functions in PHP to calculate the number of strings.
One is strlen and the other is mb_strlen;
Let's take a look at the definitions in the manual.
Strlen
Strlen-get the string length
Int strlen (string $ string)
Returns the length of a string.

Mb_strlen
Int mb_strlen (string $ str [, string $ encoding])
Returns the length of a string.
The encoding parameter is character encoding. If omitted, internal character encoding is used.

In this case, apart from mb_strlen, it seems that there is no difference in passing a character encoding. The following is an example to illustrate the difference between the two.
First look at the example:

The Code is as follows:

$ Str = 'Chinese character a 1 ';
Echo strlen ($ str ).'
'; // 14
Echo mb_strlen ($ str, 'utf8 ').'
'; // 6
Echo mb_strlen ($ str, 'gbk ').'
'; // 8
Echo mb_strlen ($ str, 'gb2312 ').'
'; // 10
?>

Result Analysis: During strlen calculation, the Chinese character of UTF8 is 3 characters in length, so the length of "Chinese character a 1 character" is 3*4 + 2 = 14, when mb_strlen is calculated, if the selected inner code is UTF8, a Chinese character will be calculated as the length of 1. Therefore, the length of "Chinese a character 1 character" is 6.
The two functions can be used to calculate the placeholder value of a string in both Chinese and English (the placeholder value of a Chinese character is 2 and that of an English character is 1)

The Code is as follows:

Echo (strlen ($ str) + mb_strlen ($ str, 'utf8')/2;

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

The Code is as follows:

Echo mb_internal_encoding ();

The built-in String Length function strlen in PHP cannot properly process Chinese strings. It only obtains the number of bytes occupied by strings. For GB2312 Chinese encoding, strlen obtains two times the number of Chinese characters, and for the UTF-8 encoding of Chinese, is three times the difference (in the UTF-8 encoding, A Chinese Character occupies 3 bytes ).

Using the mb_strlen function can better solve this problem. The usage of mb_strlen is similar to that of strlen, except that it has a second optional parameter for specifying character encoding. For example, you can use mb_strlen ($ str, 'utf-8') to get the $ str length of the UTF-8 '). If the second parameter is omitted, the internal code of PHP is 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 in Windows, make sure that it is in php. the "php_mbstring.dll" line is loaded in ini to ensure that the "extension = php_mbstring.dll" line exists and is not commented out. Otherwise, the problem of undefined functions may occur. Compile this extension in Linux.