empty Determine whether a variable is set booleanempty mixedvar empty is a language construct. This is the opposite of (boolean) var, except that no warning is generated when the variable is not set. See converting to boolean for more information. Note that this is meaningless when used on anything which isn't a variable; i.e. empty (addslashes ($name)) has no meaning since it would be checking whether something which isn't a variable is a variable with a &false; value. See also isset and unset.