Cache API: Introduce wp_cache_get_multi().

Many caching backend have support for multiple gets in a single request. This brings that support to core, with a compatability fallback that will loop over requests if needed.

Fixes: #20875.
Props: nacin, tollmanz, wonderboymusic, ryan, jeremyfelt, spacedmonkey, boonebgorges, dd32, rmccue, ocean90, jipmoors, johnjamesjacoby, tillkruess, donmhico, davidbaumwald, SergeyBiryukov, whyisjake.



git-svn-id: https://develop.svn.wordpress.org/trunk@47938 602fd350-edb4-49c9-b593-d223f7449a82

tests/phpunit/tests/cache.php

@@ -315,4 +315,23 @@ class Tests_Cache extends WP_UnitTestCase {
 		// Make sure $fake_key is not stored.
 		$this->assertFalse( wp_cache_get( $fake_key ) );
 	}
+
+	/**
+	 * @ticket 20875
+	 */
+	public function test_get_multiple() {
+		wp_cache_set( 'foo1', 'bar', 'group1' );
+		wp_cache_set( 'foo2', 'bar', 'group1' );
+		wp_cache_set( 'foo1', 'bar', 'group2' );
+
+		$found = wp_cache_get_multiple( array( 'foo1', 'foo2', 'foo3', ), 'group1' );
+
+		$expected = array(
+			'foo1' => 'bar',
+			'foo2' => 'bar',
+			'foo3' => false,
+		);
+
+		$this->assertSame( $expected, $found );
+	}
 }