php中高性能中文字符串截取函数分享

function substrs($content,$length,$add='Y'){ 
if (strlen($content)>$length) { 
if ($GLOBALS['db_charset']!='utf-8') { 
$retstr = ''; 
for ($i=0;$i<$length-2;$i++) { 
$retstr .= ord($content[$i]) > 127 ? $content[$i].$content[++$i] : $content[$i]; 
} 
return $retstr.($add=='Y' ? ' ..' : ''); 
} 
return utf8_trim(substr($content,0,$length)).($add=='Y' ? ' ..' : ''); 
} 
return $content; 
} 
function utf8_trim($str) { 
$hex = ''; 
$len = strlen($str)-1; 
for ($i=$len;$i>=0;$i-=1) { 
$ch = ord($str[$i]); 
$hex .= " $ch"; 
if (($ch & 128)==0 || ($ch & 192)==192) { 
return substr($str,0,$i); 
} 
} 
return $str.$hex; 
}
function cutstr($string, $length, $dot = ' ...') { 
global $charset; 
if(strlen($string) <= $length) { 
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; 
}