This is the easiest type. A boolean
expresses a truth value. It can be either TRUE or
FALSE.
注: The boolean type was introduced in PHP 4.
To specify a boolean literal, use either the keyword
TRUE or FALSE. Both are
case-insensitive.
Usually you use some kind of operator which returns a
boolean value, and then pass it on to a control structure.
?php // == is an operator which test // 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 you can simply type if ($show_separators) { echo " hr \n"; } ? |
To explicitly convert a value to
boolean, use either the
(bool) or the (boolean) cast.
However, in most cases you do not need to use the cast,
since a value will be automatically converted if an
operator, function or control structure requires a
boolean argument.
See also
Type Juggling.
When converting to
boolean, the following values are considered FALSE:
the
boolean FALSE
itself
the
integer 0 (zero)
the float
0.0 (zero)
an array
with zero elements
an object
with zero member variables
the special type
NULL (including unset variables)
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?php echo gettype((bool) ""); // bool(false) echo gettype((bool) 1); // bool(true) echo gettype((bool) -2); // bool(true) echo gettype((bool) "foo"); // bool(true) echo gettype((bool) 2.3e5); // bool(true) echo gettype((bool) array(12)); // bool(true) echo gettype((bool) array()); // bool(false) ? |