Conversion to boolean
The string 'true' (or 'TRUE', 'True',
and so on) in a boolean context is converted to boolean true. Any
other string in a boolean context (including 'false', '1', 'apple',
and any other) is converted to boolean false.
'true' (in an input field that requires a boolean) converts to true
'apple' (in an input field that requires a boolean) converts to false