rfc:function_autoloading

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rfc:function_autoloading [2013/08/30 12:19] – add performance section ircmaxellrfc:function_autoloading [2015/09/03 04:51] – Add streams ircmaxell
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 ====== PHP RFC: Function Autoloading ====== ====== PHP RFC: Function Autoloading ======
  
-  * Version: 0.2 +  * Version: 0.3 
-  * Date: 2013-08-29+  * Date: 2015-09-04
   * Author: Anthony Ferrara <ircmaxell@php.net>   * Author: Anthony Ferrara <ircmaxell@php.net>
   * Status: Draft   * Status: Draft
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 PHP presently offers the ability to import class-like structures (classes, interfaces and traits) via a callback (or series of them) that can be registered. This lets a developer "catch" the fact that a class isn't present, and gives them a chance to load it. This is used to great effect in the PHP community. PHP presently offers the ability to import class-like structures (classes, interfaces and traits) via a callback (or series of them) that can be registered. This lets a developer "catch" the fact that a class isn't present, and gives them a chance to load it. This is used to great effect in the PHP community.
  
-Presently, other types of symbols tables are not autoloadable. This RFC proposes a new unified autoloading mechanism to unify autoloading efforts across all three symbol tables (class, function and constant).+Presently, other types of symbols tables are not autoloadable. This RFC proposes a new unified autoloading mechanism to unify autoloading efforts across all three symbol tables (class, function, stream wrapper and constant).
  
 ===== Proposal ===== ===== Proposal =====
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 This proposal registers the following constants: This proposal registers the following constants:
  
-   * //php\AUTOLOAD_ALL => ~0// - Represents all possible autoloading types (including future ones) +  * //php\AUTOLOAD_CLASS => 1// - Represents Class autoloading 
-   * //php\AUTOLOAD_CLASS => 1// - Represents Class autoloading +  * //php\AUTOLOAD_FUNCTION => 2// - Represents Function autoloading 
-   * //php\AUTOLOAD_FUNCTION => 2// - Represents Function autoloading +  * //php\AUTOLOAD_CONSTANT => 3// - Represents Constant autoloading 
-   * //php\AUTOLOAD_CONSTANT => 4// - Represents Constant autoloading+  * //php\AUTOLOAD_STREAM = 4// - Represents Stream autoloading
  
-==== Functions ====+==== Userland Functions ====
  
-This proposal registers the following functions:+This proposal registers / modifies the following functions:
  
-=== bool php\autoload_register(callable $callback, int $type = php\AUTOLOAD_ALL, bool $prepend = false) ===+=== bool php\autoload_register(callable $callback, int $type, bool $prepend = false) ===
  
-This function behaves similar to the current //spl_autoload_register// function.+This function behaves similar to the current //spl_autoload_register// function. You *must* call this function individually for the specific autoloader that you want to hook into.
  
-=== bool php\autoload_unregister(callable $callback) ===+=== bool php\autoload_unregister(callable $callback, int $type = 0) ===
  
-This function behaves similar to the current //spl_autoload_unregister// function, and unregisters a callback that was previously registered.+This function behaves similar to the current //spl_autoload_unregister// function, and unregisters a callback that was previously registered. Note that if you registered the same callback for multiple types, this will unregister all of them unless the //$type// argument is specified.
  
-==== Behavior ====+=== array php\autoload_list(int $type) ===
  
-Registering autoloaders with the new API will allow callbacks to be fired on class, function and/or constant missing errors.+This function will return a list of all registered autoloaders for a specific type. 
  
-=== Default Behavior ===+=== function_exists() ===
  
-The default behavior is to respond to all types of missing constructs. The second parameter to the callback will be set to the value of a single constant indicating the type of construct being requested.+A new optional boolean argument is added to //function_exists()// to match the behavior of //class_exists()// when it comes to autoloading functions.
  
-<file php basic_usage.php> +=== defined() ===
-<?php +
-php\autoload_register(function($name, $type) { +
-    var_dump($name, $type); +
-    switch ($type) { +
-        case php\AUTOLOAD_FUNCTION: +
-            eval("function $name(){}"); +
-            break; +
-        case php\AUTOLOAD_CLASS: +
-            eval("class $name {}"); +
-            break; +
-        case php\AUTOLOAD_CONSTANT: +
-            define($name, $name); +
-            break; +
-    } +
-}); +
-foo(); // string(3) "foo" int(2) +
-new foo(); // string(3) "foo" int(1) +
-foo; // string(3) "foo" int(3) +
-?> +
-</file>+
  
-=== Single Type Behavior ===+A new optional boolean argument is added to //defined()// to match the behavior of //class_exists()// when it comes to autoloading constants.
  
-By passing a single constant to the register function, the callback will only be called for types that match (the //$type// parameter is still set, but will never vary).+==== Internal Typedefs ====
  
-<file php single_type.php> +This proposal adds the following internal structures:
-<?php +
-php\autoload_register(function($name, $type) { +
-    var_dump($name, $type); +
-    eval("function $name(){}"); +
-    // We don't need a switch, since we only register for functions. +
-}, php\AUTOLOAD_FUNCTION); +
-foo(); // string(3) "foo" int(2) +
-new foo(); // FATAL_ERROR +
-?> +
-</file>+
  
-=== Multiple Type Behavior ===+=== zend_autoload_func ===
  
-By passing a bitwise combination of constants to the register function, the callback will only be called for types that match.+This structure stores the autoloader function.
  
-<file php multiple_type.php> +<code c> 
-<?php +typedef struct zend_autoload_func { 
-php\autoload_register(function($name, $type) { +    zend_fcall_info fci; 
-    var_dump($name, $type); +    zend_fcall_info_cache fcc; 
-    switch ($type) { +    zval *callable; 
-        case php\AUTOLOAD_FUNCTION: +} _zend_autoload_func; 
-            eval("function $name(){}"); +</code>
-            break; +
-        case php\AUTOLOAD_CONSTANT: +
-            define($name, $name); +
-            break; +
-    } +
-}, php\AUTOLOAD_FUNCTION | php\AUTOLOAD_CONSTANT); +
-foo(); // string(3) "foo" int(2) +
-foo; // string(3) "foo" int(3) +
-new foo(); // FATAL_ERROR +
-?> +
-</file>+
  
-=== Registering The Same Callback Multiple Times ===+==== Internal Functions ====
  
-Only the first registration of a callback will succeed:+This proposal adds the following ZEND_API functions/macros:
  
-<file php single_registration.php> +=== void* zend_autoload_call(zend_string *name, zend_string *lname, int type) ===
-<?php +
-$callback = function($name, $type) { +
-    var_dump($name, $type); +
-    switch ($type) { +
-        case php\AUTOLOAD_FUNCTION: +
-            eval("function $name(){}"); +
-            break; +
-        case php\AUTOLOAD_CLASS: +
-            eval("class $name {}"); +
-            break; +
-        case php\AUTOLOAD_CONSTANT: +
-            define($name, $name); +
-            break; +
-    } +
-}; +
-php\autoload_register($callback, php\AUTOLOAD_FUNCTION); +
-php\autoload_register($callback, php\AUTOLOAD_FUNCTION | php\AUTOLOAD_CONSTANT); // returns false, as it could not be re-registered +
-foo(); // string(3) "foo" int(2) +
-foo; // FATAL_ERROR +
-?> +
-</file>+
  
-==== Performance ====+This function will call an autoloader of the specified type. It requires two versions of the name, one which is the called case, and one which is the normalized lookup case. In the case of case-sensitive constants, they should be identical. In the case of insensitive constants, functions and classes, //lname// should be a lowercase version of the name.
  
-The following benchmarks are all run on a non-debug build compiled with //--disable-all --disable-cgi//. Note that the numbers provided are the average of the 3 fastest runs for a specific test (higher numbers are thrown out).+=== int zend_autoload_register(zend_autoload_func* func, int type, int flags) ===
  
-=== Class Loading ===+This will register an autoload function with the specified flags (prepend is currently the only supported flag).
  
-1000 classes were generated, each in a single file. The following test script was used to execute the following tests:+=== int zend_autoload_unregister(zend_autoload_func* func, int type) ===
  
-<file php benchmark_autoloading.php> +This will unregister an autoloader function that's passed.
-<?php +
-spl_autoload_register(function($class) { +
-        require __DIR__ . '/files/' . $class . '.php'; +
-});+
  
-$start = microtime(true); +=== int zend_lookup_function(const char *name, int name_length, zend_function <nowiki>**</nowiki>fbc) === 
-for ($i = 0; $i < 1000; $i++) { +   
-        $class = 'test' . $i; +Lookup a function by name, using autoloading
-        new $class; +
-} +
-$end = microtime(true);+
  
-echo "Completed in " . ($end - $start) . " seconds\n"; +=== int zend_lookup_function_ex(const char *name, int name_length, const zend_literal *key, int use_autoload, zend_function <nowiki>**</nowiki>fbc) ===
-?> +
-</file>+
  
-  * Master's //spl_autoload// loader: average 0.0225 seconds to load 1000 class files. +Lookup a function by name, optionally calling the autoloader.
-  * Proposed //php\autoload_register// loader: average 0.0219 seconds to load 1000 class files. (called via spl_autoload_register)+
  
-Therefore, there is no performance regression when autoloading classes (in fact, it is slightly improved, since one additional //zend_function_call// call is removed).+=== ZEND_LOOKUP_FUNCTION_BY_NAME(name, fbc) ===
  
-=== Functions ===+This macro will find a function in the symbol table, or attempt to autoload it if not defined. The name must be a zend_string.
  
-1000 functions were generated and placed in a single file. The following test script was used to test if there was any change to function call time for a defined function:+=== ZEND_LOOKUP_FUNCTION_BY_KEY(name, key, fbc) ===
  
-<file php benchmark_functions.php> +This macro will find a function in the symbol table, or attempt to autoload it if not defined. This separates the called function in //name// from the looked up function in //key//. Both name and key must be zend_string.
-<?php +
-require_once 'functions.php';+
  
-$start = microtime(true); +=== ZEND_LOOKUP_FUNCTION_BY_NS_KEY(name, key, fbc) ===
-for ($i = 0; $i < 1000; $i++) { +
-        $func = 'test' . $i; +
-        $func(); +
-} +
-$end = microtime(true);+
  
-echo "Completed in " . ($end - $start) . " seconds\n";+This macro will find a function in the symbol table, or attempt to autoload it if not defined. This separates the called function in //name// from the looked up function in //key//. Both name and key must be zend_string. 
 + 
 +==== Behavior ==== 
 + 
 +Registering autoloaders with the new API will allow callbacks to be fired on class, function and/or constant missing errors. 
 + 
 +=== Single Type Behavior === 
 + 
 +By passing a single constant to the register function, the callback will only be called for types that match (the //$type// parameter is still set, but will never vary). 
 + 
 +<file php single_type.php> 
 +<?php 
 +php\autoload_register(function($name, $type) { 
 +    var_dump($name, $type); 
 +    eval("function $name(){}"); 
 +    // We don't need a switch, since we only register for functions. 
 +}, php\AUTOLOAD_FUNCTION); 
 +foo(); // string(3) "foo" int(2) 
 +new foo(); // FATAL_ERROR as no autoloader is registered
 ?> ?>
 </file> </file>
  
-  * Master: average 0.000216 Seconds to call 1000 functions +=== Registering The Same Callback Multiple Times For Different Types ===
-  * Proposal: average 0.000218 Seconds to call 1000 functions+
  
-Therefore, there is no performance regression to normal function calls (defined functions).+<file php multiple_registration.php> 
 +<?php 
 +$callback = function($name) { 
 +    var_dump($name); 
 +    if ($name === 'foo') { 
 +        eval("function $name(){}"); 
 +    } else { 
 +        define($name, $name); 
 +    } 
 +}; 
 +php\autoload_register($callback, php\AUTOLOAD_FUNCTION); 
 +php\autoload_register($callback, php\AUTOLOAD_CONSTANT); 
 +foo(); // string(3) "foo" int(2) 
 +FOO; // string(3) "FOO", "FOO" 
 +?> 
 +</file>
  
 ==== Userland Backwards Compatibility ==== ==== Userland Backwards Compatibility ====
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 This implementation greatly simplifies the (internal) handling of autoloading in general. This implementation greatly simplifies the (internal) handling of autoloading in general.
  
-==== Why support multiple "types" for a single autoloader? ====+==== Why not support multiple "types" for a single autoloader? ====
  
-It is more of a "why not" question. Supporting multiple types of autoloaded constructs in a single callback can result in a more flexible architecture for end users.+Existing autoloaders may support a second parameter. If we attempted to provide the type as a second argument to an existing autoloader, it could clash. This happens with the existing //spl_autoload()// autoloader. 
 + 
 +==== What Filename Conventions Does This Support? ==== 
 + 
 +None, and all. This proposal presently implements no type of file loading handler. 
 + 
 +The only thing that is implemented is the ability to register a callback to attempt to load a function or constant (or class) when it is missing. How the callback maps structures to files is outside of the scope of this RFC. 
 + 
 +==== Doesn't This Complicate The Engine? ==== 
 + 
 +Nope! The reason is that the current autoloading mechanism for classes is extremely fragile as is. 
 + 
 +For example, the implementation hinges on a global variable which sets the php-level callback to call on autoload. This requires setting up a //zend_fcall_info// struct, and a //zend_fcall_info_cache// struct, as well as dispatching a function internally to autoload. [[https://github.com/php/php-src/blob/9e17094cf4dde60432569246a9a59e48783530bb/Zend/zend_execute_API.c#L1066|The Current Implementation]]. 
 + 
 +The implementation of //spl_autoload_call// and //spl_autoload_register// are also extremely complicated. [[https://github.com/php/php-src/blob/9e17094cf4dde60432569246a9a59e48783530bb/ext/spl/php_spl.c#L466|The current SPL implementation]]. 
 + 
 +This refactor cleans both of these pieces up significantly.
  
 ===== Backward Incompatible Changes ===== ===== Backward Incompatible Changes =====
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 ===== Proposed PHP Version(s) ===== ===== Proposed PHP Version(s) =====
  
-PHP 5.6.x+PHP 7.1.x
  
 ===== SAPIs Impacted ===== ===== SAPIs Impacted =====
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 See Backward Incompatible Changes See Backward Incompatible Changes
- 
-===== New Constants ===== 
- 
-   * //php\AUTOLOAD_ALL => ~0// - Represents all possible autoloading types (including future ones) 
-   * //php\AUTOLOAD_CLASS => 1// - Represents Class autoloading 
-   * //php\AUTOLOAD_FUNCTION => 2// - Represents Function autoloading 
-   * //php\AUTOLOAD_CONSTANT => 4// - Represents Constant autoloading 
  
 ===== php.ini Defaults ===== ===== php.ini Defaults =====
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 ===== Patches and Tests ===== ===== Patches and Tests =====
  
-There is a proof-of-concept patch against PHP-5.6 (currently master) [[https://github.com/ircmaxell/php-src/compare/function-autoloading|Github Branch]]. Note that this includes the accepted but not merged implementation of [[rfc:use_function|RFC: Use Function]]. +A patch will be created shortly
- +
-This patch is not production ready, but serves as a demonstration of the functionality.+
  
 ===== References ===== ===== References =====
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   * 2013-08-29 0.1 Initial Creation   * 2013-08-29 0.1 Initial Creation
   * 2013-08-30 0.2 Add performance section and basic benchmarks   * 2013-08-30 0.2 Add performance section and basic benchmarks
 +  * 2015-09-04 0.3 Re-proposed
rfc/function_autoloading.txt · Last modified: 2017/09/22 13:28 by 127.0.0.1

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