Fix PHP notice that showed when orderby query parameter was an array (With Unit tests)

src/wp-admin/includes/class-wp-list-table.php

@@ -388,7 +388,18 @@ public function search_box( $text, $input_id ) {
 		$input_id = $input_id . '-search-input';
 
 		if ( ! empty( $_REQUEST['orderby'] ) ) {
-			echo '<input type="hidden" name="orderby" value="' . esc_attr( $_REQUEST['orderby'] ) . '" />';
+			if ( is_array( $_REQUEST['orderby'] ) ) {
+				foreach ( $_REQUEST['orderby'] as $key => $value ) {
+					/*
+					 * Orderby can be either an associative array or non-associative array.
+					 * In the latter case, this makes sure the key is a string before calling esc_attr().
+					 */
+					$key = (string) $key;
+					echo '<input type="hidden" name="orderby[' . esc_attr( $key ) . ']" value="' . esc_attr( $value ) . '" />';
+				}
+			} else {
+				echo '<input type="hidden" name="orderby" value="' . esc_attr( $_REQUEST['orderby'] ) . '" />';
+			}
 		}
 		if ( ! empty( $_REQUEST['order'] ) ) {
 			echo '<input type="hidden" name="order" value="' . esc_attr( $_REQUEST['order'] ) . '" />';
@@ -1868,4 +1879,4 @@ public function _js_vars() {
 
 		printf( "<script type='text/javascript'>list_args = %s;</script>\n", wp_json_encode( $args ) );
 	}
-}
+}

tests/phpunit/tests/admin/wpListTable.php

@@ -521,4 +521,39 @@ public function data_compat_fields() {
 			),
 		);
 	}
+
+	/**
+	 * Tests that "search_box()" works correctly with an array of orderby.
+	 *
+	 * @ticket 59494
+	 *
+	 */
+	public function test_search_box_working_with_array_of_orderby() {
+		$_REQUEST['s']       = 'search term';
+		$_REQUEST['orderby'] = array(
+			'menu_order' => 'ASC',
+			'title'      => 'ASC',
+		);
+
+		$output = get_echo( array( $this->list_table, 'search_box' ), array( 'foo Label', 59494 ) );
+
+		$expected_html1 = '<input type="hidden" name="orderby[menu_order]" value="ASC" />';
+		$expected_html2 = '<input type="hidden" name="orderby[title]" value="ASC" />';
+
+		$this->assertStringContainsString( $expected_html1, $output );
+		$this->assertStringContainsString( $expected_html2, $output );
+
+		// Test with one 'orderby' element.
+		$_REQUEST['orderby'] = array(
+			'title' => 'ASC',
+		);
+
+		$output = get_echo( array( $this->list_table, 'search_box' ), array( 'foo Label', 59494 ) );
+
+		$expected_html1 = '<input type="hidden" name="orderby[menu_order]" value="ASC" />';
+		$expected_html2 = '<input type="hidden" name="orderby[title]" value="ASC" />';
+
+		$this->assertStringNotContainsString( $expected_html1, $output );
+		$this->assertStringContainsString( $expected_html2, $output );
+	}
 }