<?php
    $a = (false && func());  // AND operator
    $a = (true || func());   // OR operator
    $a = (false and func()); // AND operator
    $a = (true or func());   // OR operator
    $a xor $b;              // XOR operator - true if either variable is true
    !$a;                    // NOT operator - true if variable is NOT true  
?>