汉语言截取无乱码的PHP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);        $offset&#43;=$count;        $chars&#43;=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&#43;&#43;;        $offset&#43;=$count;    }    return $res;}$a="中华ah人民hdj";echo utf8sub($a,5);?>

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