Description:
------------
test.php:

<?php
echo `php test.php`;
?>

//or below
<?php
echo `php test1.php`;
?>

test1.php:
<?php
echo 'test1';
?>

Expected result:
----------------
should output none or 'test1'

Actual result:
--------------
Enter the following address in the browser address bar:
'127.0.0.1/test.php',
then the entire computer CPU 100% caused the computer to die, I had to force the computer to restart.