php按字符无乱码截取中文的方法

<?php //$str 待截取的字符串 //$len 截取的字符个数 //$chars 已经截取的字符数 //$res 保存的字符串 //$chars 保存已经截取的字符串个数 //$offset 截取的偏移量 //$length 字符串的字节数 //若$len>$str的字符个数，造成无谓的while循环，($offset<$length限定) function utf8sub($str,$len){ if($len<=0){ return ; } $res=""; $offset=0; $chars=0; $length=strlen($str); while($chars<$len && $offset<$length){ $hign=decbin(ord(substr($str,$offset,1))); if(strlen($hign)<8){ $count=1; }elseif(substr($hign,0,3)=="110"){ $count=2; }elseif(substr($hign,0,4)=="1110"){ $count=3; }elseif(substr($hign,0,5)=="11110"){ $count=4; }elseif(substr($hign,0,6)=="111110"){ $count=5; }elseif(substr($hign,0,7)=="1111110"){ $count=6; } $res.=substr($str,$offset,$count); $offset+=$count; $chars+=1; } return $res; } function utf8sub1($str,$len){ $chars=0; $res=""; $offset=0; $length=strlen($str); while($chars<$len && $offset<$length){ $hign=decbin(ord(substr($str,$offset,1))); if(strlen($hign)<8){ $count=1; }elseif($hign & "11100000"=="11000000"){ $count=2; }elseif($hign & "11110000"=="11100000"){ $count=3; }elseif($hign & "11111000"=="11110000"){ $count=4; }elseif($hign & "11111100"=="11111000"){ $count=5; }elseif($hign & "11111110"=="11111100"){ $count=6; } $res.=substr($str,$offset,$count); $chars++; $offset+=$count; } return $res; } $a="中华ah人民hdj"; echo utf8sub($a,5); ?>