summary:php autoload Mechanism Analysis _php Tutorial

There are two ways to implement AutoLoad in PHP:

1. Interceptor __autoload ()

2, set the global variable function pointer autoload_func to the specified function. Typically used in C extensions

In essence, the former is still achieved through the latter.

Analysis process, PHP5.3.6 source code

=>zend/zend_vm_def.h 1894 Lines

Zend_vm_handler (109,zend_fetch_class,...

=>ZEND_EXECUTE_API.C 1526 Lines

Zend_class_entry *zend_fetch_class (const char *class_name,...

=>ZEND_EXECUTE_API.C 1564 Lines

if (ZEND_LOOKUP_CLASS_EX (Class_name,class_name_len,...

=>ZEND_EXECUTE_API.C 1039 Lines

ZEND_API int zend_lookup_class_ex (const char *na ...

=>ZEND_EXECUTE_API.C 1121 Lines

retval = Zend_call_function (&fcall_info, &fcall_cache tsrmls_cc);

=>ZEND_EXECUTE_API.C 758 Lines

Zend_call_function

As the name implies, the main function of zend_call_function is to invoke PHP functions. Its parameters fcall_info, Fcall_cache, respectively pointing to two important structures, Zend_fcall_info and Zend_fcall_info_cache

The main work flow of zend_call_function is as follows:

If Fcall_cache.function_handler is not NULL, the function that Fcall_cache.function_handler points to is executed directly.

If Fcall_cache.function_handler is null, it attempts to find a function named Fcall_info.function_name, if any, and executes it;

is summarized as follows,

The main implementation process of the autoload mechanism is:

(1) Check that the Executor global variable function pointer autoload_func is NULL.

(2) If Autoload_func is not NULL, the function directly executing the AUTOLOAD_FUNC pointer is used to load the class, and does not check whether the __autoload () function is defined.

(3) If Autoload_func is null, find out if the __autoload () function is defined in the system. If there is no definition, the error is reported and exits, and if the __autoload () function is defined, execution __autoload () attempts to load the class and returns the loading result.

Automatic loading facilitates object-oriented and code reuse, but multiple class libraries with different __autoload can cause confusion.

can be resolved with Spl_autoload, the different developer's interceptor functions are registered to the hashtable of the automatic loading function.

The mechanism for automatic loading of SPL is to maintain a hashtable that stores functions with automatic loading.

When the auto-load mechanism is triggered, Zend will traverse the function that executes the Hashtable until the class is successfully loaded or the load fails to return.

Use the function spl_autoload_register () or Spl_autoload_register (autoloadfuncitonname) when you need to use the auto-load feature

The Spl_autoload () function is loaded by default for Spl_autoload_register (), which has limited functionality and can only search the class library for the specified extension in Inlcude_path.

The Spl_autoload () function is no longer loaded by default with the Spl_autoload_register () parameter.

The function in the current auto-load Hashtable can be viewed through spl_autoload_functions (), which returns an array

Note: When using spl_autoload, the system ignores the interceptor __autoload unless explicitly using Spl_autoload_register (__autoload) to add it hashtable

Codefor

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