What is the reason for missing values ​​in the variables tab when debugging?

Question

Debugging

Good day!
Trying to set up debugging in phpstorm
Installed openserver. The site is located locally.
Debugging stops at a breakpoint, but there are no values ​​in the variables tab.

Security Code

$x = 5 + 2;

$x *= 2;

$x += 2;

echo $x;

Tell me, please, for what reason can there be no values ​​on the variables tab?