REST API: Add wp_is_numeric_array helper function

The API uses this to do special operations on list responses (used
for collections), so we need to detect whether an array is
associative or numeric-indexed.

After much discussion, the bikeshed is to be painted green and gold.

See #33982.

Built from https://develop.svn.wordpress.org/trunk@34927


git-svn-id: http://core.svn.wordpress.org/trunk@34892 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/functions.php

@@ -3176,6 +3176,24 @@ function wp_array_slice_assoc( $array, $keys ) {
 	return $slice;
 }
 
+/**
+ * Determines if the variable is a numeric-indexed array.
+ *
+ * @since 4.4.0
+ *
+ * @param mixed $data Variable to check.
+ * @return bool Whether the variable is a list.
+ */
+function wp_is_numeric_array( $data ) {
+	if ( ! is_array( $data ) ) {
+		return false;
+	}
+
+	$keys = array_keys( $data );
+	$string_keys = array_filter( $keys, 'is_string' );
+	return count( $string_keys ) === 0;
+}
+
 /**
  * Filters a list of objects, based on a set of key => value arguments.
  *

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.4-alpha-34926';
+$wp_version = '4.4-alpha-34927';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.