<script>
    function detailsmodal(rental_id){
        var data = {"rental_id" : rental_id};
        jQuery.ajax({
            url : <?=BASEURL;?>+'includes/detailsmodal.php',
            method : "post",
            data : data,
            success: function(data){
                jQuery('body').append(data);
                jQuery('#quote').modal('toggle');
            },
            error: function(){
                alert("Something went wrong!");
            }
        });
    }
</script>

jQuery('#quote').modal('show');