How to prevent same data inserted repeatedly into table? - php

Question

This is how I pass the array into the function
$rate=$data["rate"];//this is an array like rate[10,20,30,60,70]
$car->rate = $rate;
$car->rentalRate();
In the function , it accepts the array and insert into the table
public function rentalRate()
{
$rate = implode("','",$this->rate);
$sql = "INSERT INTO rental(day_1,day_3,day_7,day_15,day_30)VALUES('$rate')";
$stmt =connection::$pdo->prepare($sql);
$stmt->execute();
unset($rate);
}
Problem is,second time onwards it repeats the records. I mean for the first time when I insert only one row is inserted. The second time I insert, the same new record inserted twice. Third time I insert, thrice inserted..same goes for the number of times I insert. If I refresh than I don't have this issue.
WHat could be tracking the number of time I insert the data, could it be the array? or ajax?
This is how I submit the form via ajax
$("#submit").on("click",function()
{
$("#add_car_form").submit(function(){
var data = {
"action": "test"
};
data = $(this).serialize() + "&" + $.param(data);
$.ajax({
type: "POST",
dataType: "json",
url: "add_car_submit.php", //Relative or absolute path to response.php file
data: data,
success: function(data) {
$(".the-return").html("<br />JSON: " + data["json"] );
}
});
return false;
});
});

Answer 1

hard to say without seeing your full code but here is waht you can do:
Fist, use the dev tools on your browser and see how many requests you are submitting on every click. If they grow with every click it's your JS fault. If not then try to var_dump your POST data at the point of entry in your php scritpt. If the data is not repeated, there is a problem with your php part. (My bet would be with JS, as on AJAX request you create a new instance of php process so it can not track your submissions).