php fseek读取文件（从后往前读取）

public static function readBySeek($filepath,$lines,$revers = false){        $offset = -1;        $c = '';        $read = '';        $i = 0;        $fp = fopen($filepath, "r");        while( $lines && fseek($fp, $offset, SEEK_END) >= 0 ) {            $c = fgetc($fp);            if($c == "\n" || $c == "\r"){                $lines--;                if( $revers ){                    $read[$i] = strrev($read[$i]);                    $i++;                }            }            if( $revers ) $read[$i] .= $c;            else $read .= $c;            $offset--;        }        fclose($fp);        if( $revers ){            if($read[$i] == "\n" || $read[$i] == "\r")                array_pop($read);            else $read[$i] = strrev($read[$i]); //反转字符串            return implode('',$read);        }        return strrev(rtrim($read,"\n\r"));    }