Update PHP 72 error reporting (GoogleCloudPlatform#666)

Author: bshaffer

appengine/php72/errorreporting/README.md

@@ -1,6 +1,26 @@
 # App Engine for PHP 7.2 Error Reporting samples
 
-This app demonstrates how to report errors on on App Engine for PHP 7.2.
+This app demonstrates how to report errors on App Engine for PHP 7.2 and shows how
+different PHP error types are handled.
+
+To set up **error reporting** in your App Engine PHP 7.2 application, simply follow
+these two steps:
+
+1. Install the Google Cloud Error Reporting client library
+   ```sh
+   composer require google/cloud-error-reporting
+   ```
+2. Create a [`php.ini`](php.ini) file in the root of your project and set
+   `auto_prepend_file` to the following:
+    ```ini
+    ; in php.ini
+    auto_prepend_file=/srv/vendor/google/cloud-error-reporting/src/prepend.php
+    ```
+
+The [`prepend.php`][prepend] file will be executed prior to each request, which
+registers the client library's error handler.
+
+[prepend]: https://github.com/GoogleCloudPlatform/google-cloud-php-errorreporting/blob/master/src/prepend.php
 
 ## Setup
 

appengine/php72/errorreporting/index.php

@@ -2,8 +2,12 @@
 
 # [START gae_erroreporting_register_handler]
 # After running "composer require google/cloud-error-reporting", register the
-# error handler by including `prepend.php` in your application
-require __DIR__ . '/vendor/google/cloud-error-reporting/src/prepend.php';
+# error handler by including `prepend.php` in your application. This is most
+# easily done in `php.ini` using `auto_prepend_file`:
+#
+#    ; in your application's php.ini:
+#    auto_prepend_file=/srv/vendor/google/cloud-error-reporting/src/prepend.php
+#
 # [END gae_erroreporting_register_handler]
 
 // throw a test exception to trigger our exception handler

appengine/php72/errorreporting/php.ini

@@ -0,0 +1 @@
+auto_prepend_file=/srv/vendor/google/cloud-error-reporting/src/prepend.php