PHP currently allows users to provide type hints for functions and methods, although the type hints are currently limited to objects and arrays: http://en.wikipedia.org/wiki/Type_system#Variable_levels_of_type_checking
Restricting the type hinting to arrays and objects makes sense, as PHP's type juggling (similar in many ways to JavaScript's), a core feature of the language, performs automatic conversions between scalars as determined by context: http://php.net/manual/en/language.types.type-juggling.php However, the lack of scalar hinting does limit the ability of a developer to declare his/her intentions for function/method parameters. A non-hinted parameter expecting a scalar could be sent an object or an array, breaking the expectations (and much of the time, the functionality) of the code. That is to say, there is a value in declaring what the parameter IS NOT, too. For example, the function below could have an object or array passed as the first argument, even though the expectation is a scalar: function foo($arg){ // $arg is supposed to be a scalar and will be used as an int } *What if PHP added the hint scalar?* The example could be rewritten as: function foo(scalar $arg){ // $arg is supposed to be a scalar and will be used as an int } The idea is that the failure to send a valid scalar argument to the function would result in the same feedback that currently occurs when array or object hints are not heeded. Now, the expectations for each function/method parameter can be explicitly declared (or, at least, more explicitly.) And, *what if PHP added the following aliases for the hint scalar*: - bool - int - float - string The function could then be rewritten as below: function foo(int $arg){ // $arg is supposed to be a scalar and will be used as an int } Now, the aliases wouldn't buy any more precision in terms of PHP's parser expectations. Your function/method parameters can only expect objects, arrays, or scalars. However, the aliases would allow developers to better communicate intentions AND provide more information for IDE's and static analyses tools. And, again, the use of the scalar hint and its aliases would preclude sending objects and arrays to functions expecting otherwise. I realize this subject is heated, and people's patience has worn thin. I'm just hoping to toss out this idea I've had for some time while all of the concerns on both sides are still fresh in my head. Thanks for reading :) Adam
