From 170e2df1674910ed3e419df7cf02557425268cd9 Mon Sep 17 00:00:00 2001
From: Sergey Biryukov <sergeybiryukov@git.wordpress.org>
Date: Mon, 30 Apr 2018 03:46:07 +0000
Subject: [PATCH] General: Introduce a polyfill for `is_countable()` function
 added in PHP 7.3.

Props jrf, ayeshrajans, desrosj.
Merges [43034] to the 4.9 branch.
See #43583.

git-svn-id: https://develop.svn.wordpress.org/branches/4.9@43035 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-includes/compat.php     | 18 ++++++++++++
 tests/phpunit/tests/compat.php | 53 ++++++++++++++++++++++++++++++++++
 2 files changed, 71 insertions(+)

diff --git a/src/wp-includes/compat.php b/src/wp-includes/compat.php
index 7e37c30762..a0976c1ef2 100644
--- a/src/wp-includes/compat.php
+++ b/src/wp-includes/compat.php
@@ -497,3 +497,21 @@ endif;
 if ( ! function_exists( 'spl_autoload_register' ) ) {
 	require_once ABSPATH . WPINC . '/spl-autoload-compat.php';
 }
+
+if ( ! function_exists( 'is_countable' ) ) {
+	/**
+	 * Polyfill for is_countable() function added in PHP 7.3.
+	 *
+	 * Verify that the content of a variable is an array or an object
+	 * implementing Countable.
+	 *
+	 * @since 4.9.6
+	 *
+	 * @param mixed $var The value to check.
+	 *
+	 * @return bool True if `$var` is countable, false otherwise.
+	 */
+	function is_countable( $var ) {
+		return ( is_array( $var ) || $var instanceof Countable );
+	}
+}
diff --git a/tests/phpunit/tests/compat.php b/tests/phpunit/tests/compat.php
index 5aa749225d..1e2039b4ea 100644
--- a/tests/phpunit/tests/compat.php
+++ b/tests/phpunit/tests/compat.php
@@ -186,6 +186,50 @@ EOT;
 		$this->assertEquals( '["foo"]', $json->encodeUnsafe( array( 'foo' ) ) );
 		$this->assertEquals( array( 'foo' ), $json->decode( '["foo"]' ) );
 	}
+
+	/**
+	 * @ticket 43583
+	 */
+	function test_is_countable_availability() {
+		$this->assertTrue( function_exists( 'is_countable' ) );
+	}
+
+	/**
+	 * Test is_countable() polyfill.
+	 *
+	 * @ticket 43583
+	 *
+	 * @dataProvider countable_variable_test_data
+	 */
+	function test_is_countable_functionality( $variable, $is_countable ) {
+		$this->assertEquals( is_countable( $variable ), $is_countable );
+	}
+
+	/**
+	 * Data provider for test_is_countable_functionality().
+	 *
+	 * @ticket 43583
+	 *
+	 * @return array {
+	 *     @type array {
+	 *         @type mixed $variable     Variable to check.
+	 *         @type bool  $is_countable The expected return value of PHP 7.3 is_countable() function.
+	 *     }
+	 * }
+	 */
+	public function countable_variable_test_data() {
+		return array(
+			array( true, false ),
+			array( new stdClass(), false ),
+			array( new ArrayIteratorFake(), true ),
+			array( new CountableFake(), true ),
+			array( 16, false ),
+			array( null, false ),
+			array( array( 1, 2, 3 ), true ),
+			array( (array) 1, true ),
+			array( (object) array( 'foo', 'bar', 'baz' ), false ),
+		);
+	}
 }
 
 /* used in test_mb_substr_phpcore */ 
@@ -194,3 +238,12 @@ class classA {
 		return "Class A object";
 	}
 }
+
+class ArrayIteratorFake extends ArrayIterator {
+}
+
+class CountableFake implements Countable {
+	public function count() {
+		return 16;
+	}
+}