RFC __autodefine / spl_autodefine This proposal proposes to introduce one function for automagically defining missing definitions at run time. The reader should have a reasonable level of PHP knowledge and computer languages when reading this proposal. Note: Whenever __autodefine is used, also spl_autodefine is meant.
Current situation PHP currently supports defining missing classes by the __autoload function. This solution mimics the class loader concept from Java. Once defined, undefined class functions (methods) can be emulated by using __call and __callStatic. It can be argued that __autoload is enough for the future if the future is object-oriented. Proposition While very useful in its own right __autoload is limited: only classes can be loaded dynamically. However, there is still a lot of code that is either mixed functional and object-oriented or only functional. Excluding that code from such a solution makes life very hard on everyone maintaining mixed code bases. It is understandable that by denying this function to non-object oriented code an incentive exists for maintainers and developers to switch to object-oriented programming. Although understandable it is not acceptable, for the following reasons: 1) There are enough people maintaining and writing code in a perfect manner that do not grasp object orientation 2) Any large code base should have the possibility to slowly migrate and not be coerced into an object oriented way of working 3) Even if this coercion would work, it would not guarantee the solution is object-oriented, only that it is coded in classes So, it can be stated that a number of language constructs are missing the option to autoload. >From a conceptual point, tokens in a sequence of statements refer to definitions. The implementation of almost all run time environments demands that a definition exists before first referenced. __autoload changed this rule by allowing classes to be defined when the execution of a statement hits on an undefined class. This behaviour should be generalized. Generally, it can be said that PHP needs a mechanism for automagically defining undefined elements. The proposed name for that function is __autodefine. The parameters to this function would be $name and $type. The type parameter would refer to all the existing elements that are defined. Probably the maximal set of language constructs that could be supported are: T_ARRAY, T_CLASS, T_CLASS_C, T_CONST, T_FUNCTION T_FUNC_C, T_INCLUDE, T_INCLUDE_ONCE, T_INTERFACE, T_METHOD_C, T_NAMESPACE, T_NS_C, T_REQUIRE, T_REQUIRE_ONCE, T_USE, T_VAR, T_VARIABLE. The author believes the minimal solution should support at least T_FUNCTION, T_CLASS, T_INTERFACE and include (T_INCLUDE, T_INCLUDE_ONCE, T_REQUIRE, T_REQUIRE_ONCE). Namespaces will be part of the name as is the case in call_user_func. The relation with the current implementation is that __autoload equals __autodefine( $name, T_CLASS ) with the exception of the optional file_extensions parameter. __autoload need not be changed and __autodefine can live alongside __autoload. Author believes __autoload should be marked 'deprecated'. Minimal solution proposal __autodefine( $name, $type ) $name is the string of the missing definition $type is the integer identification of the type and defined by constants. $type constant $name format name examples T_FUNCTION [namespace][class name][::|->]function name a\b\foo, System::boot, SomeClass->getWidth T_CLASS [namespace]class name Image, ns\Image T_INTERFACE [namespace]class name Image, ns\Image T_INCLUDE file name somefile, ../somefile, \includes\Somefile T_INCLUDE_ONCE file name somefile, ../somefile, \includes\Somefile T_REQUIRE file name somefile, ../somefile, \includes\Somefile T_REQUIRE_ONCE file name somefile, ../somefile, \includes\Somefile Code examples foo(b); // __autodefine( 'foo', T_FUNCTION ) p = new PHP(); // __autodefine( 'PHP', T_CLASS ) include 'piece' // __autodefine( 'piece', T_INCLUDE ) ons\foo(); // __autodefine( 'ons\foo', T_FUNCTION ) p->im(); // __autodefine( 'PHP->im', T_FUNCTION ) p->cm(); // __autodefine( 'PHP::cm', T_FUNCTION ) Advantages A whole new array of possibilities opens up for managing code, both at run time and both at design time (development). Code is no longer bound to file containers. Small pieces of code can exist on their own. At run time only the code pieces that are needed for execution are defined. No longer parsing of complete files when only 5 code lines will be executed. A parse error in a file not relevant to the piece of code that will be executed will not prevent execution anymore. By splitting code up, developers can work side by side on the same code base, every developer on a set of code pieces, much smaller than the files now and thus reducing (locking) conflicts. Code pieces can be tested standalone and accepted. Progress is measurable on function level. Requirements can be tied to their functions. Basically, a lot of metafunctions are suddenly possible because splitting up code in smaller pieces has become a workable solution. Code could be for example managed like in a wiki, with page (= code piece) revisions etc. If needed the code pieces can be assembled into any number of files for delivery. An extreme solution is assembling all the code pieces into a zip file and having a run time implementation of __autodefine that picks definitions from a zip file. While the same code is available during development in a wiki. Large codebases can be split up over time into more manageable pieces giving the developers renewed control over their application. The __autodefine function will enable all sorts of new ways of managing code and work processes. Security can be enhanced enormously as it is not common anymore where definitions will come from and how they are decrypted. Even if someone gets access to the source code (outside the web root), it might be scrambled. Also insight into the system can be obtained by observing definition patterns that can be gathered during the autodefine processing. Disadvantages Initially execution may be slower. However, this can be countered with different implementations for __autodefine at production time and development time. The author also believes that others will find ways to counter this disadvantage by using caching or keeping definitions in memory inbetween executions. Conclusion The minimal solution to support all definitions would be the function __autodefine( $name, $type ). From there on, every developer can determine his/her own strategy for automagically defining implementations. The __autodefine function enables developers to split code up into smaller pieces as before while at the same time make it manageable by removing the need to include all these functions. By splitting code up in smaller pieces more developers can work together on one (1) code base. A parse error in a function that is not called will not damage the run time as is the case in the current implementation where many functions are grouped into files for reasons of manageability. __autodefine also enables developers to utilize all sorts of autodefinition mechanisms like retrieving definitions from the file system, the network, a zip file or even a database. Even multiple sources can be used, runtime versioning mechanisms can be utilized, code decryption on the fly is possible. It would be even interesting if the autodefinition could be in the form of byte codes. The __autodefine function is generic enough that the same concept can be applied in most other languages. The request is to supply at least the minimal __autodefine in a very near future version of PHP. To be complete and consistent spl_ autodefine_ call, spl_ autodefine_ extensions, spl_ autodefine_ functions, spl_ autodefine_ register, spl_ autodefine_ unregister and spl_ autodefine should be defined (although considered not necessary according to the author). Reinier van Loon -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php