Migrating from PHP/FI 2 to PHP 3
PHP Manual

Short-circuited boolean evaluation

In PHP 3.0 boolean evaluation is short-circuited. This means that in an expression like (1 || test_me()), the function test_me() would not be executed since nothing can change the result of the expression after the 1.

This is a minor compatibility issue, but may cause unexpected side-effects.


Migrating from PHP/FI 2 to PHP 3
PHP Manual