lithium\data\source\Database::_toBoolean()
Casts a value which is being written or compared to a boolean-type database column.
Parameters
- 
							mixed
							$valueA value of unknown type to be cast to boolean. Numeric values not equal to zero evaluate to true, otherwisefalse. String values equal to'true','t'or'T'evaluate totrue, all others tofalse. In all other cases, uses PHP's default casting.
Returns
booleanReturns a boolean representation of $value, based on the comparison rules
specified above. Database adapters may override this method if boolean type coercion
is required and falls outside the rules defined.
Source
	protected function _toBoolean($value) {
		if (is_bool($value)) {
			return $value;
		}
		if (is_int($value) || is_float($value)) {
			return ($value !== 0);
		}
		if (is_string($value)) {
			return ($value === 't' || $value === 'T' || $value === 'true');
		}
		return (boolean) $value;
	}