PHP截取中文字符串的方法

php自带的一个截取字符串的函数substr，但其只能处理英文、数字却不能截取中文混排的。如果需要在PHP中进行GB2312与UTF-8的互换，需要php_iconv.dll的支持（PHP4中包含此文件）。php5内建支持iconv，更加方便了。不管是uft-8编码转换为gb2312,还是将 gb2312 转换为 uft-8 ,PHP4.3.1以后的iconv函数很方便，只是需要自己写一个uft8到unicode的转换函数查表(gb2312.txt)。

处理函数汇总：

function cutstr($string, $length, $dot = ' ...') 
	{   //截字符串函数    GBK,UTF8
		$charset = 'utf-8';
		
		if(strlen($string) <= $length)
	 	{   //边界条件
			return $string;
		}

		$string = str_replace(array('&', '"', '<', '>'), array('&', '"', '<', '>'), $string);
		
		$strcut = '';
		if(strtolower($charset) == 'utf-8') {

			$n = $tn = $noc = 0;
			while($n < strlen($string)) {

			$t = ord($string[$n]);
			if($t == 9 || $t == 10 || (32 <= $t && $t <= 126)) {
				$tn = 1; $n++; $noc++;
			} elseif(194 <= $t && $t <= 223) {
				$tn = 2; $n += 2; $noc += 2;
			} elseif(224 <= $t && $t <= 239) {
				$tn = 3; $n += 3; $noc += 2;
			} elseif(240 <= $t && $t <= 247) {
				$tn = 4; $n += 4; $noc += 2;
			} elseif(248 <= $t && $t <= 251) {
				$tn = 5; $n += 5; $noc += 2;
			} elseif($t == 252 || $t == 253) {
				$tn = 6; $n += 6; $noc += 2;
			} else {
				$n++;
			}

			if($noc >= $length) {
				break;
			}

		}
		if($noc > $length) 
		{
			$n -= $tn;
		}

		$strcut = substr($string, 0, $n);

		} else
	 	{
			for($i = 0; $i < $length; $i++)
		 	{
				$strcut .= ord($string[$i]) > 127 ? $string[$i].$string[++$i] : $string[$i];
			}
		}
	
		$strcut = str_replace(array('&', '"', '<', '>'), array('&', '"', '<', '>'), $strcut);

		return $strcut.$dot;
	}

函数二：

function len($string, $sublen = 80, $etc = '...',$break_words = false, $middle = false)
{
$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; 
   }
}

更多知识看这位同仁的博客集合http://www.cnblogs.com/qiantuwuliang/archive/2009/07/16/1525139.html