rfc:skipparams
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rfc:skipparams [2013/09/02 07:15] – [Implementation] stas | rfc:skipparams [2015/02/08 08:12] – stas | ||
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====== Skipping optional parameters for functions ====== | ====== Skipping optional parameters for functions ====== | ||
- | * Version: | + | * Version: |
- | * Date: 2013-09-01 | + | * Date: 2015-01-01 |
* Author: Stas Malyshev < | * Author: Stas Malyshev < | ||
- | * Status: | + | * Status: |
- | * Implementation: | + | * Implementation: |
===== Introduction ===== | ===== Introduction ===== | ||
- | As PHP does not have named parameter support, a very common for function is to have many optional arguments, like this: | + | In PHP, it is very common for function is to have many optional arguments, like this: |
| | ||
Line 23: | Line 23: | ||
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. | 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 enough parameters. | + | Only declared |
===== Implementation ===== | ===== Implementation ===== | ||
- | On the engine level, it will be implemented by putting | + | On the engine level, it will be implemented by putting |
- | See example implementation | + | See example implementation |
+ | |||
+ | See tests there for examples of most common uses cases. | ||
===== User functions ===== | ===== User functions ===== | ||
Line 37: | Line 39: | ||
===== Internal functions ===== | ===== 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. | + | For internal functions, parameter parser will ignore the skipped parameters, thus leaving the defaults supplied by the caller intact. Again, skipping non-optional parameter is an error. For variadic parameters, as per above, skipping is not allowed, unless specifically requested by function declaration. |
- | Variadic functions will not return skipped parameters in argc and argv, effectively ignoring them, so: | + | Thus, this code is an error: |
| | ||
- | is the same as: | + | but this is not: |
- | var_dump(2,1); | + | call_user_func(' |
+ | |||
+ | since call_user_func is specifically described as accepting defaults. | ||
===== func_get_args() ===== | ===== func_get_args() ===== | ||
- | func_get_args() will skip parameters that are not supplied, | + | func_get_args() will use default values for parameters that are not supplied. Because of how PHP 7 engine works, it is not possible |
- | + | ||
- | | + | |
- | var_dump(func_get_args()); | + | |
- | } | + | |
- | + | ||
- | | + | |
- | + | ||
- | 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 | + | |
- | func_get_arg() will return false for parameter that was not passed. | + | |
===== call_user_func_array() ===== | ===== call_user_func_array() ===== | ||
- | call_user_func_array() will allow skipping | + | Currently, |
- | + | ||
- | call_user_func_array(' | + | |
- | + | ||
- | call_user_func | + | |
- | + | ||
- | call_user_func(' | + | |
- | + | ||
- | with the same result. | + | |
===== Internal API changes ===== | ===== Internal API changes ===== | ||
- | Parameters stored as zval** in the engine. For skipped parameter, the value stored | + | Parameters stored as array of zvals n the engine. For skipped parameter, the zval type is stored |
- | zend_parse_parameter() would ignore parameters marked as default - meaning, it will not assign any value to the underlying variable. This is unless the parameter is marked as !, in which case the parameter would be nullified just as if null were passed. This means you can not have variables marked as ! with different behavior between null and ' | + | zend_parse_parameter() would ignore parameters marked as skipped/default - meaning, it will not assign any value to the underlying variable. This is unless the parameter is marked as !, in which case the parameter would be nullified just as if null were passed. This means you can not have variables marked as ! with different behavior between null and ' |
- | For variadic | + | If certain function wants to disallow skipping |
- | If certain function wants to disallow skipping parameters, it should use option ZEND_PARSE_PARAMS_NODEFAULT with zend_parse_parameters_ex(). In this case, skipped parameters will cause . For older APIs, zend_get_parameters_array_nodefault() is available which will fail with E_WARNING " | + | ZEND_NUM_ARGS() is always the number of parameters in function call, so skipped parameters are counted there. |
- | + | ||
- | ZEND_NUM_ARGS() is always the number of parameters in function call, so skipped parameters are counted there. But trying to get a skipped parameter with API functions will produce NULL. | + | |
===== User request examples ===== | ===== User request examples ===== | ||
Line 103: | Line 78: | ||
* http:// | * http:// | ||
* http:// | * http:// | ||
+ | * http:// | ||
+ | ===== Issues raised ===== | ||
+ | |||
+ | * Internal functions that declare parameters as optional but fail to provide proper defaults and rely on ZEND_NUM_ARGS to figure out if to use default or not may be broken. The patch fixes all instances of this in the core extensions, but third-party extensions may need to be fixed too. This applies only to ones that check ZEND_NUM_ARGS() manually in the code instead of using zend_parse_parameters(). | ||
- | ===== Issues raised | + | * This RFC does not prevent named parameters implementation - in fact, a lot of cleanup to the code mentioned above is also necessary for named parameters implementation, |
- | * Support for internal functions doing manual ZEND_NUM_ARGS(). I've looked into all functions in the standard distribution, but PECL extensions that are not using zend_parse_parameters or do weird things with zval-type ones without properly initializing them or checking | + | |
+ | ===== Vote ===== | ||
+ | |||
+ | Since this RFC changes | ||
+ | |||
+ | <doodle title=" | ||
+ | * Yes | ||
+ | * No | ||
+ | </ | ||
+ | |||
+ | The vote concludes on the end of the day, PST, February 21th. | ||
===== Changelog ===== | ===== Changelog ===== | ||
Line 111: | Line 100: | ||
* 2012-04-13 First draft. | * 2012-04-13 First draft. | ||
* 2012-07-07 Changed empty parameter to use ' | * 2012-07-07 Changed empty parameter to use ' | ||
- | * Added Zend API description | + | * 2013-09-01 |
+ | * 2015-01-01 Updated for PHPNG |
rfc/skipparams.txt · Last modified: 2017/09/22 13:28 by 127.0.0.1