Hi simy202,
I guess you haven't read about operator precedence.
Please refer this: http://www.php.net/manual/en/language.operators.precedence.php
echo((1 + 2 + $var1) * $var2) / 2 - 5;
This evaluates to : (((1 + 2 + 3)*4)/2) - 5 = ((6*4)/2) - 5 = 12 - 5 = 7.
If you want it to be -8, rewrite it as:
echo((1 + 2 + $var1) * $var2) / (2 - 5);
The left of '=' sign is called Left hand side, not the left of '/' sign...