. PHP Manual . Prev . Appendix D. Migrating from PHP/FI 2 to PHP 3 . Next . 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. Prev . Home . Next . Error messages have changed . Up . Function TRUE / FALSE return values