How to write a php extension

Why use C extension

C is statically compiled, and its execution efficiency is much higher than PHP code. The performance of the same operation code, developed using C, will be hundreds of times higher than that of PHP. For IO operations such as CURL, because the time consumption is mainly on IOWait, C extension has no obvious advantage.

In addition, the C extension is loaded when the process starts. The PHP code can only operate the data of the Request life cycle. The C extension can operate in a wider range.

Recommended courses: PHP Tutorial.

Step 1

Download the source code of PHP, such as php-5.4.16. After decompression, enter the php-5.4.16\ext directory. Enter ./ext_skel –extname=myext, myext is the name of the extension, and the myext directory will be generated after execution.

ext_skel is a tool officially provided by PHP for generating PHP extension skeleton code.

cd myext. You can see several files such as php_myext.h, myext.c, config.m4, etc. config.m4 is the configuration file of the AutoConf tool, used to modify various compilation options.

The second step

Modify config.m4, change

dnl PHP_ARG_WITH(myext, for myext support,
dnl Make sure that the comment is aligned:
dnl [  --with-myext             Include myext support])

to

PHP_ARG_WITH(myext, for myext support,
[  --with-myext             Include myext support])

There is also an –enable- below myext means compiled into the php kernel. with is loaded as a dynamic link library.

Step 3

Modify php_myext.h and see PHP_FUNCTION(confirm_myext_compiled); This is the extension function declaration part. You can add a line of PHP_FUNCTION(myext_helloworld); to indicate the declaration. An extension function of myext_helloworld is created.

Then modify myext.c, which is the implementation part of the extension function.

const zend_function_entry myext_functions[] = {
        PHP_FE(confirm_myext_compiled,  NULL)           /* For testing, remove later. */
        PHP_FE(myext_helloworld,  NULL)
        PHP_FE_END      /* Must be the last line in myext_functions[] */
};

The code here is to register the function pointer to the Zend engine and add a line of PHP_FE(myext_helloworld, NULL) (do not include a semicolon after it).

Step 4

Add the execution code of myext_helloworld to the end of myext.c.

PHP_FUNCTION(myext_helloworld)
{
        char *arg = NULL;
	int arg_len, len;
	char *strg;
	if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "s", &arg, &arg_len) == FAILURE) {
		return;
	}
	php_printf("Hello World!\n");
	RETRUN_TRUE;
}

zend_parse_parameters is used to accept parameters passed in by PHP, and the RETURN_XXX macro is used to return data to PHP.

Step 5

Execute phpize, ./configure, make, and make install in sequence in the myext directory. Then modify php.ini and add extension=myext.so

Execute php -r "myext_helloworld('test');" and output hello world!

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