实用技巧：PHP截取中文字符串的问题

function FSubstr($title,$start,$len="",$magic=true) {/**  *  powered by Smartpig  *  mailto:d.einstein@263.net  */  $length = 0;if($len == "") $len = strlen($title);//判断起始为不正确位置if($start > 0){  $cnum = 0;  for($i=0;$i<$start;$i++)  {   if(ord(substr($title,$i,1)) >= 128) $cnum ++;  }  if($cnum%2 != 0) $start--;    unset($cnum);}if(strlen($title)<=$len) return substr($title,$start,$len);$alen   = 0;$blen = 0;$realnum = 0;for($i=$start;$i<strlen($title);$i++){  $ctype = 0;  $cstep = 0;  $cur = substr($title,$i,1);  if($cur == "&")  {   if(substr($title,$i,4) == "&lt;")   {    $cstep = 4;    $length += 4;    $i += 3;    $realnum ++;    if($magic)    {     $alen ++;    }   }   else if(substr($title,$i,4) == "&gt;")   {    $cstep = 4;    $length += 4;    $i += 3;    $realnum ++;    if($magic)    {     $alen ++;    }   }   else if(substr($title,$i,5) == "&amp;")   {    $cstep = 5;    $length += 5;    $i += 4;    $realnum ++;    if($magic)    {     $alen ++;    }   }   else if(substr($title,$i,6) == "&quot;")   {    $cstep = 6;    $length += 6;    $i += 5;    $realnum ++;    if($magic)    {     $alen ++;    }   }   else if(substr($title,$i,6) == "&#039;")   {    $cstep = 6;    $length += 6;    $i += 5;    $realnum ++;    if($magic)    {     $alen ++;    }   }   else if(preg_match("/&#(\d+);/i",substr($title,$i,8),$match))   {    $cstep = strlen($match[0]);    $length += strlen($match[0]);    $i += strlen($match[0])-1;    $realnum ++;    if($magic)    {     $blen ++;     $ctype = 1;    }   }  }else{   if(ord($cur)>=128)   {    $cstep = 2;    $length += 2;    $i += 1;    $realnum ++;    if($magic)    {     $blen ++;     $ctype = 1;    }   }else{    $cstep = 1;    $length +=1;    $realnum ++;    if($magic)    {     $alen++;    }   }  }    if($magic)  {   if(($blen*2+$alen) == ($len*2)) break;   if(($blen*2+$alen) == ($len*2+1))   {    if($ctype == 1)    {     $length -= $cstep;     break;    }else{     break;    }   }  }else{   if($realnum == $len) break;  }}unset($cur);unset($alen);unset($blen);unset($realnum);unset($ctype);unset($cstep);return substr($title,$start,$length);}