If you need exactly on All Posts
page, Not on All Pages
, nor All Products
or etc –
if
(
'edit.php' === $GLOBALS['pagenow']
&& (
isset( $GLOBALS['typenow'] )
&& '' == $GLOBALS['typenow']
|| 'post' == $GLOBALS['typenow']
)
)
{
// Do what you like...
}