PHP截取中文字符串函数~包括GB2312和UT-8

<?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'); 
?> 


<?php
    //截取中文字符串 
   //支持GB2312
    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; 
    } 
?> 



<?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); 
} 
?>