Build in WordPress function for fetching all registered post types: get_post_types()
<?php
// hook into init late, so everything is registered
// you can also use get_post_types where ever. Any time after init is usually fine.
add_action( 'init', 'wpse34410_init', 0, 99 );
function wpse34410_init()
{
$types = get_post_types( [], 'objects' );
foreach ( $types as $type ) {
if ( isset( $type->rewrite->slug ) ) {
// you'll probably want to do something else.
echo $type->rewrite->slug;
}
}
}
?>