php 截取字符段长度 方法

   function SubTitle($String,$Length) {  
if (mb_strwidth($String, "UTF8") <= $Length ){  
return $String;  
}else{  
$I = 0;  
$len_word = 0;  
while ($len_word < $Length){  
$StringTMP = substr($String,$I,1);  
if ( ord($StringTMP) >=224 ){  
$StringTMP = substr($String,$I,3);  
$I = $I + 3;  
$len_word = $len_word + 2;  
}elseif( ord($StringTMP) >=192 ){  
$StringTMP = substr($String,$I,2);  
$I = $I + 2;  
$len_word = $len_word + 2;  
}else{  
$I = $I + 1;  
$len_word = $len_word + 1;  
}  
$StringLast[] = $StringTMP;  
}  
/* raywang edit it for dirk for (es/index.php)*/  
if (is_array($StringLast) && !empty($StringLast)){  
$StringLast = implode("",$StringLast);  
$StringLast .= "...";  
}  
return $StringLast;   
}   
}