Re: Object method as handler functions in PHP4/Zend

Hello Zeev, On 30-Jun-99 05:58:08, you wrote: >At 03:39 30/06/99 , Manuel Lemos wrote: >>Hello Zeev, >> >>On 30-Jun-99 05:24:09, you wrote: >> >> >> >You can call an object method from outside an object in PHP 4.0, >> using the >> >> >notation of classname::method(). >> >> >> >> >Right now, only static strings are accepted for both the class name and >> >> >the method name, but we may make them dynamic so that you can this >> >> >notation indirectly. >> >> >> >>That's better, but I don't know if that solves the reentrancy problem. >> >>I'm not sure what you mean by dynamic, but I hope that means you can pass >> >>a string as name of a callback function and the function is called in the >> >>context of a user defined object of a given class. Thatr would mean that >> >>the $this references in the method function reference the functions of >> >>the class and the variables of the user defined object. >> >> >No, it doesn't mean that (I was talking about methods that don't really >> >have object contexts). Frankly, I'm not really sure what you're after. >> >You can pass that function a 'pointer' to an object, and a method name, >> >and call $object->$method(). I think you could do that in PHP 3.0, but if >> >you couldn't, you can do it using PHP 4.0. >> >>Well, to present an example that you may understand right away, think of a >>class that is used to parse a specific XML format. Ideally you would use >>the class methods as the parser's XML element and data handlers and use >>that variables of the object to store some format specific contextual >>information. >> >>In PHP 3 you can't use the class method functions as handlers. From what >>you say, that is possible in PHP 4, but you still can't store the object >>variables to store parsing contextual information. >> >>What I am after is some way to pass to the XML functions that set the >>handler functions, some reference that would let the XML parser call the >>class methods in the context of a given object. Was this clear enough? >Some pseudo-code examples of what you're after would be nice. What follows is the skelleton of a typical XML parser class: <? class xml_parser_class { var $xml_parser=0; var $error_number=0; var $error_line; var $error_column; var $error_byte_index; Function Setup() { if(!($this->xml_parser=xml_parser_create())) return(0); xml_set_element_handler($this->xml_parser,ConvertMethodToObjectFunction($this,"StartElementHandler"),ConvertMethodToObjectFunction($this,"EndElementHandler")); xml_set_character_data_handler($this->xml_parser,ConvertMethodToObjectFunction($this,"CharacterDataHandler")); return(1); } Function Parse($data,$end_of_data) { return(xml_parse($this->xml_parser,$data,$end_of_data)); } Function SetError($error) { $this->error=$error; $this->error_line=xml_get_current_line_number($this->xml_parser); $this->error_column=xml_get_current_column_number($this->xml_parser); $this->error_byte_index=xml_get_current_byte_index($this->xml_parser); } Function StartElementHandler($name,&$attrs) { test consistency if($some_error) $this->SetError($some_error); } Function EndElementHandler($name) { test consistency if($some_error) $this->SetError($some_error); } Function CharacterDataHandler($data) { test consistency if($some_error) $this->SetError($some_error); } }; ?> >If what you're after is a transparent way of passing a method&object >combination in place of a function name, and make $funcname() transparently Right. >call object->method(), no, there's no way to do it (and I think it's safe >to say there won't be one either). But why not? If you ever try to wrap a XML parser in a class you'll see the only way to work arround the current limitations of PHP is to mess a lot global variables. Not very pretty, neither not prone to name collision, which is not a good thing specially because from PHP 4 on you will be able to distribute you PHP code in compiled form without letting people tweak global names that collide. >But, if you know you're expecting an object+method/property combination, >there's nothing that stops you from calling any of these methods in the >context of the object, and access any of the object's properties, from >wherever you have the object handler and method/property names. You can do >it from both PHP code and C code. As you see from the XML call back handler example, I don't have a way to do that because XML parser expect a function name, not a class method , even less a method of specific object. Regards, Manuel Lemos Web Programming Components using PHP Classes. Look at: http://phpclasses.UpperDesign.com/ -- E-mail: mlemos@acm.org URL: http://www.mlemos.e-na.net/ PGP key: finger://mlemos@zeus.ci.ua.pt --