If you want to want to make even some characthers searchable then use ==> WHERE id like ‘%$search%’, then your can search almost everything BUT it will open up all data inside the DB and it will be displaied when emoty search is performed.
you can also use OR operator in MySQL to add some other DB fields into search ==> WHERE id=’$search’ OR first_name=’%$search’
$query = "SELECT * FROM `crud-app-tbl` WHERE id='$search' or
first_name LIKE '%$search%' or last_name LIKE '%$search%'";