PHP beginner - Can global variable be used by other page? : I try to to write

in test1.php

    <?php
    $a = 5;
    $b = 7;
    ?>

in test2.php

    <?php 
    global $a, $b;
    echo $a + $b;
    ?>

but result is 0.

So Could it be used in other page?  or should I use session ?