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+====== Skipping optional parameters for functions ======
+  * Version: 1.0
+  * Date: 2012-04-13
+  * Author: Stas Malyshev <stas@php.net>
+  * Status: Under Discussion
+  * Implementation: https://github.com/smalyshev/php-src/tree/skip_params
+===== Introduction =====
+As PHP does not have named parameter support, a very common for function is to have many optional arguments, like this:
+     function create_query($where, $order_by, $join_type='', $execute = false, $report_errors = true)
+     {...}
+If we always use defaults, it's fine. But what if we need ot change $report_errors but don't care about the others? We'd have to find function definition and copy-paste all other defaults into the call, which is annoying, error-prone and may not do what you wanted if some of the defaults change.
+===== Proposal =====
+The proposal is to allow skipping optional arguments in a call, thus making them assume default values as they do when they are not provided, like this:
+      create_query("deleted=0", "name",,, /*report_errors*/ true);
+This means that $join_type and $execute are going to use defaults.
+Of course, if we ever get implementation of named parameters, it may also solve this problem, but until we do, this can be a partial solution.
+Only optional parameters can be skipped this way, skipping non-optional one will produce the same error it does now when function is not given engough parameters.
+===== Implementation =====
+On the engine level, it will be implemented by putting NULL in the place where the parameter is passed. Functions dealing with argument handling will be updated.
+See example implementation above. Tests for most use cases will be added shortly.
+===== User functions =====
+User functions would have defaults for optional args take place of skipped arguments, just as before.
+===== Internal functions =====
+For internal functions, parameter parser will ignore the NULLs, thus leaving the defaults supplied by the caller intact. Again, skipping non-optional parameter is an error.
+Variadic functions will not return skipped parameters in argc and argv, effectively ignoring them, so:
+       var_dump(2,,1);
+is the same as:
+       var_dump(2,1);
+===== func_get_args() =====
+func_get_args() will skip parameters that are not supplied, so it would provide just the parameters that are actually supplied to the function. Thus, this code:
+     function test($a=1, $b=2, $c=3) {
+        var_dump(func_get_args());
+     }
+     test(1,,4);
+will produce:
+      array(2) {
+        [0]=>
+        int(1)
+        [2]=>
+        int(4)
+      }
+This means that if you are looping over func_get_args() result, you should use foreach() and not counter-based for().
+func_num_args() will also ignore skipped parameters and give only the number of parameters actually passed.
+func_get_arg() will return false for parameter that was not passed.
+===== call_user_func_array() =====
+call_user_func_array() will allow skipping arguments too by skipping them in supplied arguments array, like this:
+      call_user_func_array('test', array(42, 2=>43, 4=>44));
+call_user_func will allow argument skipping directly:
+      call_user_func('test', 42,,44);
+with the same result.
+===== User request examples =====
+  * http://stackoverflow.com/q/579331/214196
+  * http://stackoverflow.com/q/1115125/214196
+  * http://stackoverflow.com/q/9541776/214196
+  * http://stackoverflow.com/q/1066625/214196
+  * http://stackoverflow.com/q/4453817/214196
+  * http://stackoverflow.com/q/8356227/214196 (for Javascript)
+  * http://stackoverflow.com/q/9888725/214196
+  * http://stackoverflow.com/q/4681987/214196 (for Delphi)
+  * http://stackoverflow.com/q/4435918/214196 (for AS)
+===== Issues raised =====
+    * Using "default" instead of skipping parameter
+    * Support for internal functions doing manual ZEND_NUM_ARGS()
+===== Changelog =====
+* 2012-04-13 First draft.

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