php的扩展写法总结

1. E xtension S tructure

When writing a PHP extension, there are several key components that need to be defined and implemented. These components include:

1.1 Module Structure

The module structure acts as the entry point for the extension. It defines the module name, version, and global variables used by the extension. Here is an example of a basic module structure:

    zend_module_entry my_extension_module_entry = {
        STANDARD_MODULE_HEADER,
        "my_extension",
        NULL,
        NULL,
        NULL,
        NULL,
        NULL,
        NULL,
        NULL,
        STANDARD_MODULE_PROPERTIES_EX,
        NULL,
        NULL,
        NULL
    };
    ZEND_GET_MODULE(my_extension)

The zend_module_entry struct provides a set of functions and callbacks that can be implemented to add functionality to the extension.

1.2 Function Entry

The function entry structure defines the functions that are exposed by the extension. Each function entry consists of a name, handler function, and argument count. Here is an example of a function entry:

    zend_function_entry my_extension_functions[] = {
        PHP_FE(my_extension_hello_world, NULL)
        PHP_FE_END
    };

In this example, the my_extension_hello_world function is exposed by the extension. The PHP_FE macro is used to define the function entry, along with any required arguments.

1.3 Module Initialization

The module initialization function is called when the extension is loaded by PHP. This function is responsible for registering the module and any additional initialization tasks. Here is an example of a module initialization function:

    PHP_MINIT_FUNCTION(my_extension) {
        // Initialize any resources or data structures
        return SUCCESS;
    }

In this example, the PHP_MINIT_FUNCTION macro is used to define the module initialization function. This function should return SUCCESS if initialization is successful, or FAILURE otherwise.

2. Function Implementation

Once the extension structure is defined, you can start implementing the functions that are exposed by the extension.

2.1 Function Parameters

When implementing a function, you need to define the parameters that it accepts. The parameters are typically defined using the zend_parse_parameters function, which provides a convenient way to access and validate the passed-in arguments. Here is an example of function parameters:

    ZEND_BEGIN_ARG_INFO(arginfo_my_extension_hello_world, 0)
    ZEND_ARG_INFO(0, name)
    ZEND_END_ARG_INFO()
    PHP_FUNCTION(my_extension_hello_world) {
        char *name;
        size_t name_len;
        if (zend_parse_parameters(ZEND_NUM_ARGS(), "s", &name, &name_len) == FAILURE) {
            return;
        }
        // Function implementation
    }

In this example, the ZEND_BEGIN_ARG_INFO macro is used to define the argument information for the function. The ZEND_ARG_INFO macro is used to specify each parameter, along with its type and name. The zend_parse_parameters function is then used to extract the parameters from the PHP function call.

2.2 Return Values

When implementing a function, you also need to define the return value. The return value is typically set using the RETURN_* macros provided by the Zend Engine. Here is an example of a function with a return value:

    PHP_FUNCTION(my_extension_hello_world) {
        char *name;
        size_t name_len;
        if (zend_parse_parameters(ZEND_NUM_ARGS(), "s", &name, &name_len) == FAILURE) {
            return;
        }
        RETURN_STRING(name);
    }

In this example, the RETURN_STRING macro is used to set the return value of the function to the value of the name parameter.

3. Extending PHP

Writing a PHP extension allows you to extend the functionality of PHP by providing new functions and features. By following the extension structure and implementing the necessary functions, you can create powerful and flexible extensions that can be used in PHP applications.

It's important to note that writing a PHP extension requires a good understanding of the Zend Engine and the internals of PHP. It can be a complex and time-consuming process, but it can also be very rewarding if done correctly.

Using the extension structure and implementing the required functions, you can create custom PHP extensions that provide new functionality to your PHP applications. Whether it's adding support for a new database driver, implementing a custom caching mechanism, or providing access to a third-party API, writing a PHP extension allows you to extend the capabilities of PHP and create more powerful and flexible applications.