Index: src/wp-includes/functions.php
===================================================================
--- src/wp-includes/functions.php	(revision 28891)
+++ src/wp-includes/functions.php	(working copy)
@@ -3360,6 +3360,18 @@
 }
 
 /**
+ * Determine if the scheme of the given URL is https.
+ *
+ * @since 4.0.0
+ * 
+ * @param  string  $url The URL
+ * @return boolean      True if the given URL uses https, false if not (or if the URL is not valid).
+ */
+function is_https_url( $url ) {
+	return ( 'https' === parse_url( $url, PHP_URL_SCHEME ) );
+}
+
+/**
  * Whether SSL login should be forced.
  *
  * @since 2.6.0
Index: tests/phpunit/tests/functions/isHttpsUrl.php
===================================================================
--- tests/phpunit/tests/functions/isHttpsUrl.php	(revision 0)
+++ tests/phpunit/tests/functions/isHttpsUrl.php	(working copy)
@@ -0,0 +1,22 @@
+<?php
+
+/**
+ * Test is_https_url().
+ *
+ * @group functions.php
+ * @ticket 28487
+ */
+class Tests_Functions_IsHttpsUrl extends WP_UnitTestCase {
+
+	function test_is_https_url() {
+
+		$this->assertTrue( is_https_url( 'https://example.com/' ) );
+		$this->assertTrue( is_https_url( 'https://localhost/' ) );
+
+		$this->assertFalse( is_https_url( 'http://example.com' ) );
+		$this->assertFalse( is_https_url( 'Hello World!' ) );
+		$this->assertFalse( is_https_url( 'httpsinvalid' ) );
+
+	}
+
+}