add flatbuffers

commit 6da1cf79d90eb242e7da5318241d42279a3df3ba
Author: Max Burke <max@urbanlogiq.com>
Date:   Sun Jan 19 14:47:28 2020 -0800

    [rust] Add use declarations to Rust-generated bindings for imported FB definitions (#5645)

    * Bugfix for Rust generation of union fields named with language keywords

flatbuffers/docs/source/PHPUsage.md

@@ -0,0 +1,89 @@
+Use in PHP    {#flatbuffers_guide_use_php}
+==========
+
+## Before you get started
+
+Before diving into the FlatBuffers usage in PHP, it should be noted that
+the [Tutorial](@ref flatbuffers_guide_tutorial) page has a complete guide to
+general FlatBuffers usage in all of the supported languages
+(including PHP). This page is specifically designed to cover the nuances of
+FlatBuffers usage in PHP.
+
+You should also have read the [Building](@ref flatbuffers_guide_building)
+documentation to build `flatc` and should be familiar with
+[Using the schema compiler](@ref flatbuffers_guide_using_schema_compiler) and
+[Writing a schema](@ref flatbuffers_guide_writing_schema).
+
+## FlatBuffers PHP library code location
+
+The code for FlatBuffers PHP library can be found at `flatbuffers/php`. You
+can browse the library code on the [FlatBuffers
+GitHub page](https://github.com/google/flatbuffers/tree/master/php).
+
+## Testing the FlatBuffers JavaScript library
+
+The code to test the PHP library can be found at `flatbuffers/tests`.
+The test code itself is located in [phpTest.php](https://github.com/google/
+flatbuffers/blob/master/tests/phpTest.php).
+
+You can run the test with `php phpTest.php` from the command line.
+
+*Note: The PHP test file requires
+[PHP](http://php.net/manual/en/install.php) to be installed.*
+
+## Using theFlatBuffers PHP library
+
+*Note: See [Tutorial](@ref flatbuffers_guide_tutorial) for a more in-depth
+example of how to use FlatBuffers in PHP.*
+
+FlatBuffers supports both reading and writing FlatBuffers in PHP.
+
+To use FlatBuffers in your own code, first generate PHP classes from your schema
+with the `--php` option to `flatc`. Then you can include both FlatBuffers and
+the generated code to read or write a FlatBuffer.
+
+For example, here is how you would read a FlatBuffer binary file in PHP:
+First, include the library and generated code (using the PSR `autoload`
+function). Then you can read a FlatBuffer binary file, which you
+pass the contents of to the `GetRootAsMonster` function:
+
+~~~{.php}
+  // It is recommended that your use PSR autoload when using FlatBuffers in PHP.
+  // Here is an example:
+  function __autoload($class_name) {
+    // The last segment of the class name matches the file name.
+    $class = substr($class_name, strrpos($class_name, "\\") + 1);
+    $root_dir = join(DIRECTORY_SEPARATOR, array(dirname(dirname(__FILE__)))); // `flatbuffers` root.
+
+    // Contains the `*.php` files for the FlatBuffers library and the `flatc` generated files.
+    $paths = array(join(DIRECTORY_SEPARATOR, array($root_dir, "php")),
+                   join(DIRECTORY_SEPARATOR, array($root_dir, "tests", "MyGame", "Example")));
+    foreach ($paths as $path) {
+      $file = join(DIRECTORY_SEPARATOR, array($path, $class . ".php"));
+      if (file_exists($file)) {
+        require($file);
+        break;
+    }
+  }
+
+  // Read the contents of the FlatBuffer binary file.
+  $filename = "monster.dat";
+  $handle = fopen($filename, "rb");
+  $contents = $fread($handle, filesize($filename));
+  fclose($handle);
+
+  // Pass the contents to `GetRootAsMonster`.
+  $monster = \MyGame\Example\Monster::GetRootAsMonster($contents);
+~~~
+
+Now you can access values like this:
+
+~~~{.php}
+  $hp = $monster->GetHp();
+  $pos = $monster->GetPos();
+~~~
+
+## Text Parsing
+
+There currently is no support for parsing text (Schema's and JSON) directly
+from PHP.