Creating a query for trapping datetime in multiple room PHP - php

Question

I have a scheduling system
I have a query to create a error if the date and time has already been scheduled
my problem is i have multiple room and if i create a schedule in one room if it is the same with the other room it wont add
function save_schedule(){
extract($_POST);
$data = "";
foreach($_POST as $k=> $v){
if($k != 'id'){
if(!empty($data)) $data.=", ";
$data.=" {$k} = '{$v}'";
}
}
if(strtotime($datetime_end) < strtotime($datetime_start)){
$resp['status'] = 'failed';
$resp['err_msg'] = "Date and Time Schedule is Invalid.";
}else{
$d_start = strtotime($datetime_start);
$d_end = strtotime($datetime_end);
$chk = $this->conn->query("SELECT * FROM `schedule_list` where (('{$d_start}'
Between unix_timestamp(datetime_start) and unix_timestamp(datetime_end)) or ('{$d_end}'
Between unix_timestamp(datetime_start) and unix_timestamp(datetime_end))) ".(($id > 0) ? "
and id !='{$id}' " : ""))->num_rows;
if($chk > 0){
$resp['status'] = 'failed';
$resp['err_msg'] = "The schedule is conflict with other schedules.";
}else{
if(empty($id)){
$sql = "INSERT INTO `schedule_list` set {$data}";
}else{
$sql = "UPDATE `schedule_list` set {$data} where id = '{$id}'";
}
$save = $this->conn->query($sql);
if($save){
$resp['status'] = 'success';
$this->settings->set_flashdata('success', " Schedule successfully saved.");
}else{
$resp['status'] = 'failed';
$resp['sql'] = $sql;
$resp['qry_error'] = $this->conn->error;
$resp['err_msg'] = "There's an error while submitting the data.";
}
}
}
return json_encode($resp);
}
can anyone help me in this query
$chk = $this->conn->query("SELECT * FROM `schedule_list` where (('{$d_start}'
Between unix_timestamp(datetime_start) and unix_timestamp(datetime_end)) or ('{$d_end}'
Between unix_timestamp(datetime_start) and unix_timestamp(datetime_end))) ".(($id > 0) ? "
and id !='{$id}' " : ""))->num_rows;
assembly_hall table
schedule_list table

Answer 1

Aside from the SQL injection problems, I see a couple of issues:
Your query should be only looking for conflicts for the assembly_hall_id it will be inserting; as is, it looks for conflicting schedules for any assembly hall.
Your conflict check is incorrect; if a hall is reserved for 1pm-2pm and someone tries to reserve it for 12pm-3pm, you don't detect it, because neither the new start nor end is in the reserved range. Correct conflict checking is done with:
least(datetime_end, new end value) > greatest(datetime_start, new start value)