Build a PHP Extension from Scratch with PHP7: A Step‑by‑Step Guide

This article uses PHP7 as a base to explain how to create a PHP extension from zero, implementing a say function that prints "hello word".

Step 1: Generate the Extension Skeleton

PHP provides the ext_skel tool in the ./ext directory of the source tree to generate basic extension code.

$ cd php_src/ext/
$ ./ext_skel --extname=say

The --extname value becomes the extension name, and a directory named say is created.

Step 2: Edit config.m4

The config.m4 file works with phpize to produce a configure script that checks the build environment. Open the file and adjust the comments:

dnl If your extension references something external, use with:
 dnl PHP_ARG_WITH(say, for say support,
 dnl   [  --with-say          Include say support])

 dnl Otherwise use enable:
 dnl PHP_ARG_ENABLE(say, whether to enable say support,
 dnl   [  --enable-say        Enable say support])

Since this extension has no external dependencies, remove the comment marker before the PHP_ARG_ENABLE block.

Step 3: Implement the Extension Code

Modify say.c to add the say function:

PHP_FUNCTION(say)
{
    zend_string *strg;
    strg = strpprintf(0, "hello word");
    RETURN_STR(strg);
}

Register the function in the function entry list:

PHP_FE(say, NULL)       /* For testing, remove later. */
PHP_FE(confirm_say_compiled, NULL) /* For testing, remove later. */
PHP_FE_END  /* Must be the last line in say_functions[] */

Step 4: Compile and Install

Run the standard build steps:

$ phpize
$ ./configure
$ make && make install

Add the extension to php.ini:

[say]
extension = say.so

After installation, verify the extension is loaded with php -m, which should list say.

Step 5: Test the Extension

Create a PHP script that calls say() and confirm the output matches the expected "hello word".