wp-admin/includes/class-wp-filesystem-ftpsockets.php:587Gets the file modification time.
$filestringint|false public function mtime( $file ) { $modified_time = $this->ftp->mdtm( $file ); if ( false === $modified_time ) { return false; } return (int) $modified_time; }Introduced in 2.5.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-admin/includes/class-wp-filesystem-ftpsockets.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.