$foo = True; // assign the value TRUE to $foo
// == is an operator which tests
// equality and returns a boolean
if ($action == "show_version") {
    echo "The version is 1.23";

// this is not necessary...
if ($show_separators == TRUE) {
    echo "<hr>\n";

// ...because this can be used with exactly the same meaning:
if ($show_separators) {
    echo "<hr>\n";
  • This is the simplest type.
  • Expresses a truth value.
  • It can be either TRUE or FALSE.
  • To specify a boolean literal, use the constants TRUE or FALSE. Both are case-insensitive.
  • Typically, the result of an operator which returns a boolean value is passed on to a control structure.

Converting to boolean

To explicitly convert a value to boolean, use the (bool) or (boolean) casts.

In most cases the cast is unnecessary, since a value will be automatically converted if an operator, function or control structure requires a boolean argument.

boolean — Structure map

Clickable & Draggable!

boolean — Related pages: