Fix --pretty-print generating invalid PHP when messages array is empty

features/makephp.feature

@@ -363,3 +363,40 @@ Feature: Generate PHP files from PO files
       JS Only Translation
       """
 
+  Scenario: Should create valid PHP files with pretty-print when there are no translations
+    Given an empty foo-plugin directory
+    And a foo-plugin/foo-plugin-de_DE.po file:
+      """
+      # Copyright (C) 2018 Foo Plugin
+      # This file is distributed under the same license as the Foo Plugin package.
+      msgid ""
+      msgstr ""
+      "Project-Id-Version: Foo Plugin\n"
+      "Report-Msgid-Bugs-To: https://wordpress.org/support/plugin/foo-plugin\n"
+      "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
+      "Language-Team: LANGUAGE <LL@li.org>\n"
+      "Language: de_DE\n"
+      "MIME-Version: 1.0\n"
+      "Content-Type: text/plain; charset=UTF-8\n"
+      "Content-Transfer-Encoding: 8bit\n"
+      "POT-Creation-Date: 2018-05-02T22:06:24+00:00\n"
+      "PO-Revision-Date: 2018-05-02T22:06:24+00:00\n"
+      "X-Domain: foo-plugin\n"
+      "Plural-Forms: nplurals=2; plural=(n != 1);\n"
+      """
+
+    When I run `wp i18n make-php foo-plugin --pretty-print`
+    Then STDOUT should contain:
+      """
+      Success: Created 1 file.
+      """
+    And the return code should be 0
+    And the foo-plugin/foo-plugin-de_DE.l10n.php file should contain:
+      """
+      	'messages' => [],
+      """
+    And the foo-plugin/foo-plugin-de_DE.l10n.php file should not contain:
+      """
+      [,
+      """
+

src/PhpArrayGenerator.php

@@ -174,6 +174,10 @@ private static function var_export( $value, $pretty_print = false, $indent_level
 				}
 			}
 
+			if ( empty( $entries ) ) {
+				return '[]';
+			}
+
 			return '[' . PHP_EOL . implode( $separator, $entries ) . ',' . PHP_EOL . $closing_indent . ']';
 		} else {
 			foreach ( $value as $key => $val ) {