t4018: add missing test cases for PHP

A later patch changes the built-in PHP pattern. These test cases
demonstrate aspects of the pattern that we do not want to change.

Signed-off-by: Kana Natsuno <dev@whileimautomaton.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t4018/php-class

@@ -0,0 +1,4 @@
+class RIGHT
+{
+    const FOO = 'ChangeMe';
+}

t/t4018/php-function

@@ -0,0 +1,4 @@
+function RIGHT()
+{
+    return 'ChangeMe';
+}

t/t4018/php-method

@@ -0,0 +1,7 @@
+class Klass
+{
+    public static function RIGHT()
+    {
+        return 'ChangeMe';
+    }
+}