Posts, Post Types: Avoid a PHP warning when get_the_content() is called outside of the loop.

This ensures that `$pages` and other globals are only used after they have been set up in `setup_postdata()`.

Follow-up to [44941].

Props tessawatkinsllc, dontdream, spacedmonkey, squarecandy, davidbaumwald, SergeyBiryukov.
Fixes #47824. See #42814.

git-svn-id: https://develop.svn.wordpress.org/trunk@48114 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/class-wp-query.php

@@ -4275,7 +4275,7 @@ class WP_Query {
 		$numpages     = $elements['numpages'];
 
 		/**
-		 * Fires once the post data has been setup.
+		 * Fires once the post data has been set up.
 		 *
 		 * @since 2.8.0
 		 * @since 4.1.0 Introduced `$this` parameter.

src/wp-includes/post-template.php

@@ -282,7 +282,9 @@ function get_the_content( $more_link_text = null, $strip_teaser = false, $post =
 		return '';
 	}
 
-	if ( null === $post ) {
+	// Use the globals if the $post parameter was not specified,
+	// but only after they have been set up in setup_postdata().
+	if ( null === $post && did_action( 'the_post' ) ) {
 		$elements = compact( 'page', 'more', 'preview', 'pages', 'multipage' );
 	} else {
 		$elements = generate_postdata( $_post );

tests/phpunit/tests/post/getTheContent.php

@@ -75,4 +75,13 @@ class Tests_Post_GetTheContent extends WP_UnitTestCase {
 
 		$this->assertSame( 'Bang', $found );
 	}
+
+	/**
+	 * @ticket 47824
+	 */
+	public function test_should_fall_back_to_post_global_outside_of_the_loop() {
+		$GLOBALS['post'] = self::factory()->post->create( array( 'post_content' => 'Foo' ) );
+
+		$this->assertSame( 'Foo', get_the_content() );
+	}
 }