(I've posted this to the PHP newsgroups, as well, but as many here might not read them, I post here, as well. I hope that's not considered "overboard", and if so, please let me know) To round off my trilogy of "why"'s about PHP... :) If this subject have been discussed before, I'd appreciate a pointer to it. I again haven't found it in a search of the PHP groups. The PHP manual mentions "overloading" (http://www.php.net/manual/en/language.oop5.overloading.php), but it isn't really overloading at all... Not in the sense it's used in other languages supporting overloading (such as C++ and Java). As one of the user-contributed notes on that page says, it would be more appropriate to call it "dynamic methods and properties". What "overloading" in PHP is about, is to be able to do $object-><name>(...), and it will call the built-in function __call() with <name> and an array of the parameters. Since "overloading" is used in this rather confusing sense (compared to other languages) in PHP, it may be useful with a brief recap of how it works in C++ and Java. In these languages, overloading means that you may have several (member or non-member) functions with the same name, as long as their signature is different (number and type of arguments). Translated to PHP, this could look like this: function f($a) {...} // #1 function f($a, $b) {...} // #2 function f($a, b$, $c) {...} // #3 function f(Person $a) {...} // # 4 f(1); // Calls #1 f(1,"test"); // Calls #2 f(1,2,3); // Calls #3 $obj=new Person(); f($obj); // Calls #4 The last call would technically also match #1, but the one with type hint (Person) might be considered "more specialised". This issue has, like type hints for built-in types, been asked in a Zend Q & A, such as this one: http://www.zend.com/expert_qa/qas.php?id=10&single=1 --- Start quote --- public Object child() { return this.child; } public Object child(Object p_child) { this.child = p_child; return this.child(); } So this is what you call function overloading? Questions: - Why is it called function overloading? - Why won't it be supported in PHP? (important) It is called function overloading because you have two instances of the same function name but they differ only by the function arguments. You expect the right one to be called according to the arguments. It won't be supported by PHP because it doesn't fit in with its dynamically typed value paradigm and execution methodology. However, you may reach similar affects by using optional function arguments for example: public Object child(Object p_child=NULL) { if (p_child != NULL) { this.child = p_child; } return this.child; } --- End quote --- Again, I don't find the answer satisfactory, but perhaps someone here can convince me? Even if PHP has loose/weak typing, then as for type hints for built-in types, a value or variable has a specific type at any one time. At the very least, one might provide overloading for functions taking arguments of user-defined types (objects), in the same way as one provide optional static typing in the form of type hints. I.e.: function print(Person $p) {...} function print(Something $s) {...} Comments? Regards, Terje -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
