As Sally highlights, you can use in_array() like this (untested):
// target ids
$ids = array(123, 321, 213);
if (!empty($post->ID) && is_numeric($post->ID) && in_array((int)$post->ID, $ids)) {
// do jazz
} else {
// do stuff
}
As Sally highlights, you can use in_array() like this (untested):
// target ids
$ids = array(123, 321, 213);
if (!empty($post->ID) && is_numeric($post->ID) && in_array((int)$post->ID, $ids)) {
// do jazz
} else {
// do stuff
}