If you use PHP for application scripting e.g. in conjunction with PHP-GTK there is no limitation in accessing and manipulating visual objects through COM.
Generally it is, but as PHP is mostly used as a web scripting language it runs in the web servers context, thus visual objects will never appear on the servers desktop. If you use PHP for application scripting e.g. in conjunction with PHP-GTK there is no limitation in accessing and manipulating visual objects through COM.