standards/php.md - Add a TLDR example

To see actual examples of the coding style, you need to skim multiple blurbs
and click multiple links, and the eventual page shows very isolated
examples.

This revision adds a brief example so that a new contributor can get a
general sense of the layout immediately.

(Note: It's not possible for a brief example to show every edge-case, and we
shouldn't try -- that's why the commit also emphasizes the link into the
relevant examples from d.o docs.)

docs/standards/php.md

@@ -3,6 +3,55 @@
 CiviCRM uses the [Drupal Coding Standards](https://www.drupal.org/docs/develop/standards) as a basis for the coding standards used in civicrm-core code and in civicrm-drupal code.
 The standards are version-independent and all new code should follow the current standards regardless of version. 
 
+## Brief example
+
+```php
+/**
+ * The example class demonstrates Drupal/Civi code convention.
+ */
+class CRM_Coding_Example implements CRM_Coding_ExampleInterface {
+
+  /**
+   * Increase the size of a file exponentially.
+   *
+   * @param string $file
+   *   The full file path. (Ex: '/tmp/myfile.txt')
+   * @param int $power
+   *   The number of times to double the size.
+   * @return bool
+   *   Whether the operation succeeded.
+   */
+  public function expandFile($file, $power) {
+    $keyValuePairs = array(
+      'first' => 1,
+      'second' => 2,
+    );
+
+    if ($power < 4) {
+      echo "You got it, boss.\n";
+    }
+    elseif ($power < 10) {
+      echo "Whoa, that's gonna be a big file!\n";
+    }
+    else {
+      echo "Whoa, that's gonna be a really big file!\n";
+    }
+
+    for ($i = 0; $i < $power; $i++) {
+      $oldContent = file_get_contents($file);
+      if (file_put_contents($file, $oldContent . $oldContent) === FALSE) {
+        return FALSE;
+      }
+    }
+
+    return TRUE;
+  }
+
+}
+```
+
+For more details, see [the full series of example snippets](https://www.drupal.org/docs/develop/standards/coding-standards) from `drupal.org`.
+
 ## Deviations from the Drupal Coding Standards {:#vs-drupal}
 
 There are two deviations from the Drupal Coding standards that apply in CiviCRM.