Index: wp-includes/functions.php
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- wp-includes/functions.php	(revision 42ff9456498e65f74d39848992f871020b6909ea)
+++ wp-includes/functions.php	(revision )
@@ -844,6 +844,37 @@
 }
 
 /**
+ * Get an item from a query string.
+ *
+ * @since 4.4.0
+ *
+ * @param string|array $key   Query key or keys to remove.
+ * @param bool|string  $query Optional. When false uses the current URL. Default false.
+ *
+ * @return string|null Value of key item
+ */
+
+function get_query_arg( $key, $query = false ) {
+
+	if ( $query === false) {
+		$query = $_SERVER['REQUEST_URI'];
+	}
+
+	$url = parse_url( $query );
+
+	if ( isset( $url['query'] ) ) {
+
+		parse_str( $url['query'], $output );
+
+		if ( isset( $output[ $key ] ) ) {
+			return $output[ $key ];
+		}
+	}
+
+	return null;
+}
+
+/**
  * Returns an array of single-use query variable names that can be removed from a URL.
  *
  * @since 4.4.0