PHP example: bool is_bool(mixed)

$x = 1 == 1; // boolean value if (is_bool($x)) { echo "\$x contains a boolean.\n"; } else { echo "\$x does not contain a boolean.\n"; // Never executed } $x = 1; if (is_bool($x)) { echo "\$x contains a boolean.\n"; // Never executed } else { echo "\$x does not contain a boolean.\n"; }