常见字符串截取函数

1. 截取GB2312字符用的函数

<?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 <wwccss@263.net>
* @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 = "book.chinaz.com -- 站长书库、站长教程";
$Length = "18";
$Append = false;
echo sysSubStr($String,$Length,$Append);
?>