解析如何用php screw加密php源代码

vi my_screw.h
 -- Please change the encryption SEED key (pm9screw_mycryptkey) into the
    values according to what you like.
    The encryption will be harder to break, if you add more values to the
    encryption SEED array. However, the size of the SEED is unrelated to
    the time of the decrypt processing.
 *  If you can read and understand the source code, to modify an original
        encryption logic will be possible. But in general, this should not
        be necessary.
   OPTIONAL: Encrypted scripts get a stamp added to the beginning of the
        file. If you like, you may change this stamp defined by
        PM9SCREW and PM9SCREW_LEN in php_screw.h. PM9SCREW_LEN must
        be less than or equal to the size of PM9SCREW.

<?
$a=0;
$t=time();
for($i=0;$i<5000000;$i++)
  {$a=$a*$i;}
$t1=time();
echo "<p>";
echo "It used:";
echo $t1-$t;
echo "seconds";
?>