Add examples and README

This is the first commit. Examples:

- Game Boy
- Game Boy + SDL 2
- SNES
- SNES + SDL 2
- GTK 3
- Java
- PHP Plus
- Text to Speech

.gitignore

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+*.bin
+.DS_Store
+*.dylib
+*.gb
+*.gbc
+*.smc

README.md

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+# Awesome PHP FFI
+
+[![Software License](https://img.shields.io/badge/license-MIT-brightgreen.svg?style=flat)](http://gabrielrcouto.mit-license.org/)
+
+This is a repository showing some use cases of [PHP FFI](https://wiki.php.net/rfc/ffi).
+
+Examples in this repository:
+
+- [Game Boy Emulator](gameboy)
+- [Game Boy Emulator with SDL2 rendering](gameboy-sdl)
+- [GTK3 window with a button](gtk3)
+- [Calling a function from .class Java file](java-itaucripto)
+- [Modifying the PHP Core to auto inject PHP Open Tag](php-plus)
+- [Simple printf example](printf)
+- [Creating window and rendering pixels with SDL2](sdl)
+- [SNES Emulator](snes)
+- [SNES Emulator with SDL2 rendering](snes-sdl)
+- [text-to-speech using Mac library](speech)
+
+Other repositories about PHP FFI:
+
+- [DBus access via FFI and PHP 7.4 POC](https://github.com/paxal/php-dbus)
+- [Driving webview using PHP 7.4 FFI](https://github.com/andyvanee/php-webview-ffi)
+- [PHP wrapper for libsass using FFI](https://github.com/shyim/php-sass)
+- [PHP TensorFlow Binding](https://github.com/dstogov/php-tensorflow)
+- [FFIMe](https://github.com/ircmaxell/FFIMe)
+- [A compiler. For PHP](https://github.com/ircmaxell/php-compiler)

gameboy-sdl/README.md

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+# Game Boy Emulator + SDL2
+
+![sameboy-sdl](https://user-images.githubusercontent.com/2197005/65930680-fab53280-e3dc-11e9-98bb-f02c6cd94368.gif)
+
+This example uses the sameboy library for Game Boy emulation + SDL2 library for rendering.
+
+You'll need to compile the [sameboy library](https://github.com/LIJI32/SameBoy) and change the `FFI_LIB` on `sameboy_libretro.h` file.
+
+You'll need to install the [SDL2 library](https://www.libsdl.org/download-2.0.php) and change the `FFI_LIB` on `sdl.h` file.

gameboy-sdl/run.php

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+<?php
+const ROM = 'pokemon.gbc';
+
+const RETRO_ENVIRONMENT_SET_PIXEL_FORMAT = 10;
+const RETRO_ENVIRONMENT_GET_VARIABLE = 15;
+const RETRO_ENVIRONMENT_GET_VARIABLE_UPDATE = 17;
+const RETRO_ENVIRONMENT_GET_RUMBLE_INTERFACE = 23;
+const RETRO_ENVIRONMENT_GET_LOG_INTERFACE = 27;
+
+const RETRO_DEVICE_ID_JOYPAD_B = 0;
+const RETRO_DEVICE_ID_JOYPAD_Y = 1;
+const RETRO_DEVICE_ID_JOYPAD_SELECT = 2;
+const RETRO_DEVICE_ID_JOYPAD_START = 3;
+const RETRO_DEVICE_ID_JOYPAD_UP = 4;
+const RETRO_DEVICE_ID_JOYPAD_DOWN = 5;
+const RETRO_DEVICE_ID_JOYPAD_LEFT = 6;
+const RETRO_DEVICE_ID_JOYPAD_RIGHT = 7;
+const RETRO_DEVICE_ID_JOYPAD_A = 8;
+const RETRO_DEVICE_ID_JOYPAD_X = 9;
+const RETRO_DEVICE_ID_JOYPAD_L = 10;
+const RETRO_DEVICE_ID_JOYPAD_R = 11;
+const RETRO_DEVICE_ID_JOYPAD_L2 = 12;
+const RETRO_DEVICE_ID_JOYPAD_R2 = 13;
+const RETRO_DEVICE_ID_JOYPAD_L3 = 14;
+const RETRO_DEVICE_ID_JOYPAD_R3 = 15;
+
+const KEYBOARD_MAPPING = [
+    RETRO_DEVICE_ID_JOYPAD_RIGHT => 'd',
+    RETRO_DEVICE_ID_JOYPAD_LEFT => 'a',
+    RETRO_DEVICE_ID_JOYPAD_UP => 'w',
+    RETRO_DEVICE_ID_JOYPAD_DOWN => 's',
+    RETRO_DEVICE_ID_JOYPAD_A => ',',
+    RETRO_DEVICE_ID_JOYPAD_B => '.',
+    RETRO_DEVICE_ID_JOYPAD_SELECT => 'n',
+    RETRO_DEVICE_ID_JOYPAD_START => 'm'
+];
+
+const SDL_INIT_VIDEO = 0x00000020;
+const SDL_RENDERER_ACCELERATED = 0x00000002;
+const SDL_RENDERER_PRESENTVSYNC = 0x00000004;
+const SDL_QUIT = 0x100;
+const SDL_WINDOW_SHOWN = 0x00000004;
+
+const ZOOM_LEVEL = 4;
+const SCREEN_HEIGHT = 144;
+const SCREEN_WIDTH = 160;
+
+$currentSecond = 0;
+$fps = 0;
+$framesInSecond = 0;
+
+$sdl = FFI::load('sdl.h');
+$sameboy = FFI::load('sameboy_libretro.h');
+
+if ($sdl->SDL_Init(SDL_INIT_VIDEO) != 0) {
+    throw new Exception('SDL_Init Error: ' . $sdl->SDL_GetError(), 1);
+}
+
+$win = $sdl->SDL_CreateWindow('PHP FFI Boy', 0, 0, SCREEN_WIDTH * ZOOM_LEVEL, SCREEN_HEIGHT * ZOOM_LEVEL, SDL_WINDOW_SHOWN);
+
+if ($win == null){
+    throw new Exception('SDL_CreateWindow Error: ' . $sdl->SDL_GetError(), 1);
+    $sdl->SDL_Quit();
+}
+
+$ren = $sdl->SDL_CreateRenderer($win, -1, 0);
+
+$sdl->SDL_SetRenderDrawColor($ren, 0, 0, 0, 255);
+$sdl->SDL_RenderClear($ren);
+
+$event = $sdl->new('SDL_Event', false);
+
+$gameinfo = $sameboy->new('struct retro_game_info', false);
+$gameinfo->path = $sameboy->strdup(ROM);
+
+$sameboy->retro_set_environment(function($cmd, $data) use ($sameboy) {
+    if ($cmd === RETRO_ENVIRONMENT_SET_PIXEL_FORMAT) {
+        return true;
+    }
+
+    if ($cmd === RETRO_ENVIRONMENT_GET_VARIABLE) {
+        $argument = $sameboy->cast('struct retro_variable', $data);
+
+        if ($argument->key === 'sameboy_model') {
+            $argument->value = $sameboy->strdup('Game Boy');
+            $data = FFI::addr($argument);
+        }
+
+        return true;
+    }
+
+    if ($cmd === RETRO_ENVIRONMENT_GET_VARIABLE_UPDATE) {
+        $argument = $sameboy->cast('bool', $data);
+        $data = FFI::addr($argument);
+        return false;
+    }
+
+    if ($cmd === RETRO_ENVIRONMENT_GET_RUMBLE_INTERFACE) {
+        $argument = $sameboy->cast('struct retro_rumble_interface', $data);
+        $argument->set_rumble_state = function($port, $effect, $strength) {
+            return;
+        };
+        $data = FFI::addr($argument);
+        return false;
+    }
+
+    if ($cmd === RETRO_ENVIRONMENT_GET_LOG_INTERFACE) {
+        return false;
+    }
+
+    return;
+});
+
+$sameboy->retro_set_audio_sample(function($a, $b) {
+    return;
+});
+
+$sameboy->retro_set_input_poll(function () {
+    return;
+});
+
+$sameboy->retro_set_input_state(function ($port, $device, $index, $id) use (&$key) {
+    if ($key === KEYBOARD_MAPPING[$id]) {
+        return true;
+    }
+
+    return false;
+});
+
+$sameboy->retro_set_video_refresh(function ($data, $width, $height, $pitch) use (&$ren, $sdl) {
+    $pixels = FFI::cast('uint32_t[' . ($width * $height) . ']', $data);
+
+    $sdl->SDL_SetRenderDrawColor($ren, 142, 134, 9, 255);
+    $sdl->SDL_RenderClear($ren);
+    $sdl->SDL_SetRenderDrawColor($ren, 37, 57, 61, 255);
+
+    for ($y = 0; $y < SCREEN_HEIGHT; $y++) {
+        for ($x = 0; $x < SCREEN_WIDTH; $x++) {
+            $pixel = $pixels[$x + (SCREEN_WIDTH * $y)];
+
+            if ($pixel === 0) {
+                $rect = $sdl->new('SDL_Rect', true);
+                $rect->x = $x * ZOOM_LEVEL;
+                $rect->y = $y * ZOOM_LEVEL;
+                $rect->w = $rect->h = ZOOM_LEVEL;
+                $sdl->SDL_RenderFillRect($ren, FFI::addr($rect));
+                $sdl->SDL_RenderDrawRect($ren, FFI::addr($rect));
+            }
+        }
+    }
+
+    $sdl->SDL_RenderPresent($ren);
+
+    return;
+});
+
+$sameboy->retro_init();
+$sameboy->retro_load_game(FFI::addr($gameinfo));
+
+$isRunning = true;
+
+while ($isRunning) {
+    //Calculate current FPS
+    if ($currentSecond != time()) {
+        $fps = $framesInSecond;
+        $currentSecond = time();
+        $framesInSecond = 1;
+    } else {
+        ++$framesInSecond;
+    }
+
+    $sameboy->retro_run();
+
+    if ($sdl->SDL_PollEvent(FFI::addr($event))) {
+        if ($event->type == SDL_QUIT) {
+            $isRunning = false;
+        }
+    }
+
+    $sdl->SDL_SetWindowTitle($win, 'PHP FFI Boy - FPS: ' . $fps);
+}

gameboy-sdl/sameboy_libretro.h

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+#define FFI_LIB "sameboy_libretro.dylib"
+
+int sprintf(char *str, const char *format, ...);
+char *strdup(const char *s);
+
+typedef void (*retro_audio_sample_t)(int16_t left, int16_t right);
+typedef bool (*retro_environment_t)(unsigned cmd, void *data);
+typedef void (*retro_input_poll_t)(void);
+typedef int16_t (*retro_input_state_t)(unsigned port, unsigned device, unsigned index, unsigned id);
+typedef void (*retro_log_printf_t)(enum retro_log_level level, const char *fmt, ...);
+typedef bool (*retro_set_rumble_state_t)(unsigned port, enum retro_rumble_effect effect, uint16_t strength);
+typedef void (*retro_video_refresh_t)(const void *data, unsigned width, unsigned height, size_t pitch);
+
+bool vblank1_occurred = false, vblank2_occurred = false;
+
+void retro_init(void);
+unsigned retro_api_version(void);
+bool retro_load_game(const struct retro_game_info *info);
+void retro_run(void);
+
+void retro_set_audio_sample(retro_audio_sample_t cb);
+
+void retro_set_environment(retro_environment_t cb);
+
+void retro_set_input_poll(retro_input_poll_t cb);
+void retro_set_input_state(retro_input_state_t cb);
+
+void retro_set_video_refresh(retro_video_refresh_t cb);
+
+struct retro_game_info
+{
+   const char *path;       /* Path to game, UTF-8 encoded.
+                            * Usually used as a reference.
+                            * May be NULL if rom was loaded from stdin
+                            * or similar. 
+                            * retro_system_info::need_fullpath guaranteed 
+                            * that this path is valid. */
+   const void *data;       /* Memory buffer of loaded game. Will be NULL 
+                            * if need_fullpath was set. */
+   size_t      size;       /* Size of memory buffer. */
+   const char *meta;       /* String of implementation specific meta-data. */
+};
+
+struct retro_rumble_interface
+{
+   retro_set_rumble_state_t set_rumble_state;
+};
+
+struct retro_variable
+{
+   /* Variable to query in RETRO_ENVIRONMENT_GET_VARIABLE.
+    * If NULL, obtains the complete environment string if more 
+    * complex parsing is necessary.
+    * The environment string is formatted as key-value pairs 
+    * delimited by semicolons as so:
+    * "key1=value1;key2=value2;..."
+    */
+   const char *key;
+
+   /* Value to be obtained. If key does not exist, it is set to NULL. */
+   const char *value;
+};