PHP & MYSQL -- dont insert same data

Question

I need your help. I’m stuck at a point from where I can’t figure it out that how to stop a product to be booked twice a day on a web form.

I have 41 products to rent out on daily basis.

My problem is: if a client books a product #4 (pg_no) and date 26-06-2017 then another client isn't able to book the same product for the same period of time.

If a client selects the same product and date, then a message should appear saying "already booked - please select another date"

Also, do I have to define anything on database level?

Your help will be highly appreciated.

Please note: this rule is only for product # (pg_no) and date fields are not allow for the same day.

<?php
//connecting string
include("dbconnect.php");
//assigning
$pg_no=$_REQUEST['pg_no'];
$name=$_REQUEST['Name'];
$tele=$_REQUEST['Tele'];
$city=$_REQUEST['City'];
$date=$_REQUEST['Date'];   

//checking if pg_no and Date are same 
 $check=mysqli_query($db_connect,"SELECT * FROM lstclient WHERE pg_no='{$pg_no}', Date='{$date}'");

     if(mysqli_fetch_row($check) ==0)
     {
        echo "Already booked  please select another date<br/>";
     }
   //if not the insert data
    else
     {          
      $query=mysqli_query($db_connect,"INSERT INTO lstclient(pg_no,Name,Tele,City,Date) VALUES('$pg_no','$name','$tele','$city','$date')") or die(mysql_error());
      }
      mysqli_close($db_connect);

   // messaging 
     if($query)
        {
             header("location:index.php?note=failed");
        }
        else
        {
             header("location:index.php?note=success");
        }

    ?>

You have blatant SQL injections, if this will ever run on a server connected to the real internet you must escape any input that you get from a $_REQUEST before using it to build a SQL string. I escape everything, and it works great. Automated bots will find this and eat your site for breakfast. — wedstrom
– wedstrom, Commented Jul 7, 2017 at 15:39

Chris Forrence · Accepted Answer · 2017-07-07 14:41:11Z

1

Create a UNIQUE KEY constraint on your table between the two columns.

ALTER TABLE lstclient ADD CONSTRAINT `pg_no_date` UNIQUE (pg_no, date)

Then when you try to insert a row that violates this constraint mysql will throw an error. You should catch this MySQL error and respond with the correct error.

if( mysqli_errno() == 1062) {
    // Duplicate key error
}

edited Jul 7, 2017 at 14:41

Chris Forrence

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answered Jun 25, 2017 at 20:42

Ryan Tuosto

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1 Comment

php 101 guy Over a year ago

thanks-- phpd and ryan for your help. one more issue, could you please tell me how to fix -- echo "Already booked please select another date<br/>";

phpd · Accepted Answer · 2017-06-26 01:45:55Z

0

Add a unique key to your lstclient table like ryan suggested. Also, your check query has syntax error, it should be like below.

SELECT * FROM lstclient WHERE pg_no='{$pg_no}' AND Date='{$date}'

answered Jun 26, 2017 at 1:45

phpd

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