字符串截取是一个非常常见的编程任务，而往往带中文的字符串截取会经常用到。虽然不难，但是自己写函数实现又耗费时间，这里介绍一个比较好用的字符串截取函数，能够胜任基本的需求了。

1. 截取GB2312中文字符串

< ?php

//截取中文字符串

function mysubstr($str, $start, $len) {

$tmpstr = "";

$strlen = $start + $len;

for($i = 0; $i < $strlen; $i++) {

if(ord(substr($str, $i, 1)) > 0xa0) {

$tmpstr .= substr($str, $i, 2);

$i++;

} else

$tmpstr .= substr($str, $i, 1);

}

return $tmpstr;

}

?>

2. 截取utf8编码的多字节字符串

< ?php

//截取utf8字符串

function utf8Substr($str, $from, $len)

{

return preg_replace('#^(?:[\x00-\x7F]|[\xC0-\xFF][\x80-\xBF]+){0,'.$from.'}'.

'((?:[\x00-\x7F]|[\xC0-\xFF][\x80-\xBF]+){0,'.$len.'}).*#s',

'$1',$str);

}

?>

3. UTF-8、GB2312都支持的汉字截取函数

< ?php

/*

Utf-8、gb2312都支持的汉字截取函数

cut_str(字符串, 截取长度, 开始长度, 编码);

编码默认为 utf-8

开始长度默认为 0

*/

function cut_str($string, $sublen, $start = 0, $code = 'UTF-8')

{

if($code == 'UTF-8')

{

$pa = "/[\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]/";

preg_match_all($pa, $string, $t_string);

if(count($t_string[0]) - $start > $sublen) return join('', array_slice($t_string[0], $start, $sublen))."...";

return join('', array_slice($t_string[0], $start, $sublen));

}

else

{

$start = $start*2;

$sublen = $sublen*2;

$strlen = strlen($string);

$tmpstr = '';

for($i=0; $i< $strlen; $i++)

{

if($i>=$start && $i< ($start+$sublen))

{

if(ord(substr($string, $i, 1))>129)

{

$tmpstr.= substr($string, $i, 2);

}

else

{

$tmpstr.= substr($string, $i, 1);

}

}

if(ord(substr($string, $i, 1))>129) $i++;

}

if(strlen($tmpstr)< $strlen ) $tmpstr.= "...";

return $tmpstr;

}

}

$str = "abcd需要截取的字符串";

echo cut_str($str, 8, 0, 'gb2312');

?>

4. BugFree 的字符截取函数

< ?php

/**

* @package BugFree

* @version $Id: FunctionsMain.inc.php,v 1.32 2005/09/24 11:38:37 wwccss Exp $

*

*

* Return part of a string(Enhance the function substr())

*

* @author Chunsheng Wang

* @param string $String the string to cut.

* @param int $Length the length of returned string.

* @param booble $Append whether append "...": false|true

* @return string the cutted string.

*/

function sysSubStr($String,$Length,$Append = false)

{

if (strlen($String) < = $Length )

{

return $String;

}

else

{

$I = 0;

while ($I < $Length)

{

$StringTMP = substr($String,$I,1);

if ( ord($StringTMP) >=224 )

{

$StringTMP = substr($String,$I,3);

$I = $I + 3;

}

elseif( ord($StringTMP) >=192 )

{

$StringTMP = substr($String,$I,2);

$I = $I + 2;

}

else

{

$I = $I + 1;

}

$StringLast[] = $StringTMP;

}

$StringLast = implode("",$StringLast);

if($Append)

{

$StringLast .= "...";

}

return $StringLast;

}

}

$String = "17test.info 走在中国自动化测试的前沿";

$Length = "18";

$Append = false;

echo sysSubStr($String,$Length,$Append);

?>