Code:
$rip = $_SERVER['REMOTE_ADDR'];
$sd  = time();
$count = 1;

$file1 = "ip.txt";
$lines = file($file1);
$line2 = "";

foreach ($lines as $line_num => $line)
    {
        //echo $line."<br>";
        $fp = strpos($line,'****');
        $nam = substr($line,0,$fp);
        $sp = strpos($line,'++++');
        $val = substr($line,$fp+4,$sp-($fp+4));
        $diff = $sd-$val;
        if($diff < 300 && $nam != $rip)
            {
             $count = $count+1;
             $line2 = $line2.$line;
             //echo $line2; 
            }
    }

$my = $rip."****".$sd."++++\n";
$open1 = fopen($file1, "w");
fwrite($open1,"$line2");
fwrite($open1,"$my");
fclose($open1);

echo $count
?>