Efficient Chinese string truncation Functions

When using the traditional string truncation function substr in PHP to process strings containing Chinese characters, Chinese characters are cut off. When PHP extension libraries can be used, we can use mb_substr instead. However, it is difficult for the extension library to be connected. in Linux, PHP needs to be re-compiled. Sometimes it cannot be done, not to mention its many redundant functions.
You can see many functions that implement this function on the network. However, many algorithms use loop judgment, which is very inefficient when strings are large.
Here we will introduce two efficient functions: c_substr and m_substr. Their usage is exactly the same as that of substr and mb_substr. The difference is that c_substr is calculated by byte, that is, the length of a Chinese character is 2; m_substr is calculated by word, that is, the length of a Chinese character is 1. Optional as needed.

Code: function c_substr ($ STR, $ start = 0 ){
$ CHR = CHR (127 );
$ P = array ("/[/x81-/xfe] ([/x81-/xfe] | [/X40-/xfe])/", "/[/x01-/x77]/");
$ R = array ("","");
If (func_num_args ()> 2)
$ End = func_get_arg (2 );
Else
$ End = strlen ($ Str );
If ($ start <0)
$ Start + = $ end;

If ($ Start> 0 ){
$ S = substr ($ STR, 0, $ start );
If ($ s [strlen ($ S)-1]> $ ch ){
$ S = preg_replace ($ P, $ R, $ S );
$ Start + = strlen ($ S );
}
}
$ S = substr ($ STR, $ start, $ end );
$ End = strlen ($ S );
If ($ s [$ end-1]> $ ch ){
$ S = preg_replace ($ P, $ R, $ S );
$ End + = strlen ($ S );
}
Return substr ($ STR, $ start, $ end );
}

Function m_substr ($ STR, $ start ){
Preg_match_all ("/[/X80-/xFF]?. /", $ STR, $ AR );
If (func_num_args ()> = 3 ){
$ End = func_get_arg (2 );
Return join ("", array_slice ($ ar [0], $ start, $ end ));
} Else
Return join ("", array_slice ($ ar [0], $ start ));
}

Windix Feng has also rewritten A UTF-8 that is applicable and also documented together. For later use. Function utf8_substr2 ($ STR, $ start ){
/*
The UTF-8 version of substr (), for people who can't use mb_substr () like me.
Length is not the Count of bytes, but the Count of UTF-8 characters

Author: windix Feng
Bug report to: windix (AT) 263.net, http://www.douzi.org/blog

-History-
1.0 initial version
2.0 use preg instead of strcmp and cycles, speed up!
*/

Preg_match_all ("/[/x01-/x7f] | [/xc2-/xdf] [/X80-/xbf] |/xe0 [/xa0-/xbf] [/X80- /xbf] | [/xe1-/XeF] [/X80-/xbf] [/X80-/xbf] |/xf0 [/x90-/xbf] [/X80 -/ xbf] [/X80-/xbf] | [/xf1-/xf7] [/X80-/xbf] [/X80-/xbf] [/X80-/xbf]/", $ STR, $ AR );

If (func_num_args ()> = 3 ){
$ End = func_get_arg (2 );
Return join ("", array_slice ($ ar [0], $ start, $ end ));
} Else {
Return join ("", array_slice ($ ar [0], $ start ));
}
}