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