PHP Manual-Language Reference-type-boolean Boolean type

1. Boolean expresses the true value, which can be false. Two are not case-sensitive.

2. The result of the Boolean value returned by the operator is usually passed to the control flow .

3. When converting to Boolean, the following values are considered false:

3.1 Boolean value false itself

3.2 Integer value 0

3.3 Floating-point value 0.0

3.4 Empty string, and string "0"

3.5 Arrays that do not include any elements

3.6 Objects that do not include any member variables (PHP 4.0 applies only)

3.7 Special type NULL (including variables that have not been assigned)

3.8 SimpleXML object generated from an empty tag

4. To explicitly convert a value to Boolean, use either (BOOL) or (Boolean) to cast. However, they are usually converted automatically.

PHP Manual-Language Reference-type-boolean Boolean type