Advanced techniques and debugging methods for developing PHP7/8 extensions with C++

C Advanced techniques and debugging methods for developing PHP7/8 extensions

Introduction:
In Web development, PHP is a commonly used programming language. However, sometimes we need to use C to write high-performance extensions for lower-level interactions and operations with PHP. This article will introduce some advanced techniques and debugging methods for developing PHP7/8 extensions in C to help developers make better use of this powerful tool.

1. The basic structure of the extension
   Before we start writing PHP extensions, we need to understand the basic structure of the extension. An extension usually contains the following parts:

#include <php.h>

// 定义模块信息
ZEND_BEGIN_MODULE_GLOBALS(example)
    char *greeting;
ZEND_END_MODULE_GLOBALS(example)

ZEND_DECLARE_MODULE_GLOBALS(example)

// 函数声明
PHP_FUNCTION(example_hello);

// 定义扩展信息
ZEND_BEGIN_ARG_INFO(arginfo_example_hello, 0)
    ZEND_ARG_INFO(0, name)
ZEND_END_ARG_INFO()

zend_function_entry example_functions[] = {
    PHP_FE(example_hello, arginfo_example_hello)
    {NULL, NULL, NULL}
};

zend_module_entry example_module_entry = {
    STANDARD_MODULE_HEADER,
    "example",
    example_functions,
    NULL,
    NULL,
    NULL,
    NULL,
    NULL,
    NO_VERSION_YET,
    STANDARD_MODULE_PROPERTIES
};

#ifdef COMPILE_DL_PHPEXAMPLE
    ZEND_GET_MODULE(example)
#endif

// 初始化全局变量
static void php_example_init_globals(zend_example_globals *example_globals)
{
    example_globals->greeting = NULL;
}

// 模块初始化和销毁函数
PHP_MINIT_FUNCTION(example)
{
    ZEND_INIT_MODULE_GLOBALS(example, php_example_init_globals, NULL);
    return SUCCESS;
}

PHP_MSHUTDOWN_FUNCTION(example)
{
    return SUCCESS;
}

PHP_RINIT_FUNCTION(example)
{
    return SUCCESS;
}

PHP_RSHUTDOWN_FUNCTION(example)
{
    return SUCCESS;
}

PHP_MINFO_FUNCTION(example)
{
    php_info_print_table_start();
    php_info_print_table_row(2, "Example support", "enabled");
    php_info_print_table_end();
}

// 定义函数
PHP_FUNCTION(example_hello)
{
    char *name = NULL;
    size_t name_len;
    if (zend_parse_parameters(ZEND_NUM_ARGS(), "s", &name, &name_len) == FAILURE) {
        return;
    }
    php_printf("Hello, %s!", name);
}

2. C and PHP type conversion
   Type conversion is required when passing parameters and returning values ​​between C and PHP . Here are some common conversion methods:

• Convert PHP string to C string:

zend_string *str = Z_STR_P(arg);
std::string cpp_str(str->val, str->len);

• Convert C string to PHP String:

zval ret;
ZVAL_STRING(&ret, cpp_str.c_str());
return ret;

• Convert PHP array to C array:

HashTable *ht = Z_ARRVAL_P(arg);
ZEND_HASH_FOREACH_VAL(ht, val) {
    zval *elem = val;
    // 使用elem进行操作
} ZEND_HASH_FOREACH_END();

• Convert C array to PHP array:

zval arr;
array_init(&arr);
for (const auto& elem : cpp_arr) {
    add_next_index_string(&arr, elem.c_str());
}
return arr;

3. Debugging PHP extensions
   When we develop PHP extensions, sometimes we need to debug to find problems. Here are some methods for debugging extensions:

• Use PHP’s php_printf function to output debugging information:

php_printf("Debug message: %s
", message);

• Settings debug flag, and enable extended debugging mode:

#ifdef PHP_EXAMPLE_DEBUG
    #define EXAMPLE_DEBUG 1
#else
    #define EXAMPLE_DEBUG 0
#endif

// 启用调试模式
if (EXAMPLE_DEBUG) {
    zend_string *debug_str = strpprintf(0, "Debug mode is enabled");
    php_error(E_NOTICE, "%s", debug_str->val);
    zend_string_release(debug_str);
}

• Use GDB for debugging. First, you need to include debugging information when compiling the extension:

$ phpize
$ ./configure --enable-example-phpdebug
$ make

Then use GDB to debug the extension:

$ gdb --args php -d extension=/path/to/example.so -r 'echo example_hello("World");'
(gdb) run

• Use Valgrind for memory detection:

$ valgrind --tool=memcheck php -d extension=/path/to/example.so -r 'echo example_hello("World");'

Conclusion:
This article introduces some advanced techniques and debugging methods for developing PHP7/8 extensions in C. Mastering these skills and methods can help developers better use C to write high-performance PHP extensions and solve problems encountered during the extension development process. I hope this article will be helpful to you in the process of developing PHP extensions in C.

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