added readme

Author: thbley

.gitignore

@@ -1,2 +1,5 @@
 *.so
 *.h
+.buildpath
+.project
+.settings/

ackermann.php

@@ -32,7 +32,7 @@
  * Combining PHP and Go gives a lot of new opportunities.
  *
  * Writing and integrating PHP extensions based on C/C++ can be difficult and time consuming.
- * This can be made easier and more flexible using Go and PHP-FFI.
+ * This can be made easier and more flexible using Go libraries and PHP-FFI.
  */
 
 error_reporting(E_ALL);

readme.md

@@ -0,0 +1,33 @@
+PHP Example to integrate Go using PHP-FFI
+------------------------------------------
+
+Go is a statically typed, compiled programming language that offers more performance and concurrency.
+Combining PHP and Go gives a lot of new opportunities.
+
+Writing and integrating PHP extensions based on C/C++ can be difficult and time consuming.
+This can be made easier and more flexible using Go libraries and PHP-FFI.
+
+Go code can compiled as a shared object file (.so) and loaded in PHP using PHP-FFI.
+(see https://www.php.net/manual/en/book.ffi.php)
+
+This example compares the performance of PHP and Go using implementations
+of the recursive ackermann function (see https://en.wikipedia.org/wiki/Ackermann_function).
+In this example Go 1.14 is 27 times faster than PHP 7.4.
+
+Usage:
+
+    go build -o ackermann.so -buildmode=c-shared ackermann.go
+
+    php ackermann.php
+
+Requirements:
+
+    Go package (https://golang.org/dl/)
+
+    PHP 7.4+
+
+Notes:
+
+PHP-FFI can automatically convert basic Go types (long, char*) into PHP types.
+For using more complex data structures, I'm also providing an example (ackermann_json)
+using JSON strings as input and output.