A face question _php skill about PHP variable reference

The questions about the PHP face question are as follows:

Copy Code code as follows:

<?php
$a = 1;
$x =& $a;
$b = $a + +;
?>

Ask:
What are the values of $b and $x respectively?

The answer to the PHP interview question is as follows:
$b = 1;
$x = 2;

Do you understand? Don't understand, think again. When one variable equals the reference of another, either side changes its value and the value that the other sees changes. The former add this time to show, and then add the next time will be shown.