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. Usually used in c extensions
Essentially, the former is achieved through the latter.
Analysis process, PHP5.3.6 source code
=>Zend/zend_vm_def.h Line 1894
ZEND_VM_HANDLER(109,ZEND_FETCH_CLASS,...
=>zend_execute_API.c line 1526
zend_class_entry *zend_fetch_class(const char *class_name,...
=>zend_execute_API.c line 1564
if(zend_lookup_class_ex(class_name,class_name_len,...
=>zend_execute_API.c line 1039
ZEND_API int zend_lookup_class_ex(const char *na...
=>zend_execute_API.c line 1121
retval = zend_call_function(&fcall_info, &fcall_cache TSRMLS_CC);
=>zend_execute_API.c line 758
zend_call_function
As the name suggests, the main function of zend_call_function is to call PHP functions. Its parameters fcall_info and fcall_cache point to two important structures respectively, zend_fcall_info and zend_fcall_info_cache
The main workflow of zend_call_function is as follows:
If fcall_cache.function_handler is not NULL, execute the function pointed to by fcall_cache.function_handler directly.
If fcall_cache.function_handler is NULL, try to find a function named fcall_info.function_name, and if it exists, execute it;
is summarized as follows,
The main execution process of the autoload mechanism is:
(1) Check whether the executor global variable function pointer autoload_func is NULL.
(2) If autoload_func is not NULL, the function pointed to by the autoload_func pointer is directly executed to load the class without checking whether the __autoload() function is defined.
(3) If autoload_func is NULL, check whether the __autoload() function is defined in the system. If it is not defined, an error is reported and exits; if the __autoload() function is defined, __autoload() is executed to try to load the class and the loading result is returned.
Automatic loading facilitates object-oriented and code reuse, but different __autoloads in multiple class libraries can cause confusion.
It can be solved with spl_autoload, which registers the interceptor functions of different developers into the hashtable of the automatic loading function.
The mechanism by which spl implements automatic loading is to maintain a hashtable, which stores various functions with automatic loading function.
When the automatic loading mechanism is triggered, zend will traverse and execute the functions in this hashtable until the class is successfully loaded or returns after the loading fails.
When you need to use the autoload function, use the function spl_autoload_register() or spl_autoload_register(autoloadfuncitonname)
Spl_autoload_register() without parameters will load the spl_autoload() function by default. This function has limited functions and can only search for the class library with the specified extension in inlcude_path.
The spl_autoload_register() with parameters no longer loads the spl_autoload() function by default.
You can view the functions in the current autoload hashtable through spl_autoload_functions(), which returns an array
Note: When using spl_autoload, the system will ignore the interceptor __autoload unless it is explicitly added to the hashtable using spl_autoload_register(__autoload)
Codefor

PHP is mainly procedural programming, but also supports object-oriented programming (OOP); Python supports a variety of paradigms, including OOP, functional and procedural programming. PHP is suitable for web development, and Python is suitable for a variety of applications such as data analysis and machine learning.

PHP originated in 1994 and was developed by RasmusLerdorf. It was originally used to track website visitors and gradually evolved into a server-side scripting language and was widely used in web development. Python was developed by Guidovan Rossum in the late 1980s and was first released in 1991. It emphasizes code readability and simplicity, and is suitable for scientific computing, data analysis and other fields.

PHP is suitable for web development and rapid prototyping, and Python is suitable for data science and machine learning. 1.PHP is used for dynamic web development, with simple syntax and suitable for rapid development. 2. Python has concise syntax, is suitable for multiple fields, and has a strong library ecosystem.

PHP remains important in the modernization process because it supports a large number of websites and applications and adapts to development needs through frameworks. 1.PHP7 improves performance and introduces new features. 2. Modern frameworks such as Laravel, Symfony and CodeIgniter simplify development and improve code quality. 3. Performance optimization and best practices further improve application efficiency.

PHPhassignificantlyimpactedwebdevelopmentandextendsbeyondit.1)ItpowersmajorplatformslikeWordPressandexcelsindatabaseinteractions.2)PHP'sadaptabilityallowsittoscaleforlargeapplicationsusingframeworkslikeLaravel.3)Beyondweb,PHPisusedincommand-linescrip

PHP type prompts to improve code quality and readability. 1) Scalar type tips: Since PHP7.0, basic data types are allowed to be specified in function parameters, such as int, float, etc. 2) Return type prompt: Ensure the consistency of the function return value type. 3) Union type prompt: Since PHP8.0, multiple types are allowed to be specified in function parameters or return values. 4) Nullable type prompt: Allows to include null values and handle functions that may return null values.

In PHP, use the clone keyword to create a copy of the object and customize the cloning behavior through the \_\_clone magic method. 1. Use the clone keyword to make a shallow copy, cloning the object's properties but not the object's properties. 2. The \_\_clone method can deeply copy nested objects to avoid shallow copying problems. 3. Pay attention to avoid circular references and performance problems in cloning, and optimize cloning operations to improve efficiency.

PHP is suitable for web development and content management systems, and Python is suitable for data science, machine learning and automation scripts. 1.PHP performs well in building fast and scalable websites and applications and is commonly used in CMS such as WordPress. 2. Python has performed outstandingly in the fields of data science and machine learning, with rich libraries such as NumPy and TensorFlow.


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