PDO Insert foreach - php

Question

I am trying to insert an array of values multiple times into a table.
I have a simple array that is generated by a user checking a box and that's what gets added to the array, I then want to insert each value into a table, I thought I could do it with a foreach loop and iterate $i but it appears I can't, I don't need to worry about security or anything as this is internally used by two people.
here is what I have:
foreach($detailsinvoice as $desc){
$conn3 = new PDO( DB_DSN, DB_USERNAME, DB_PASSWORD );
$sql3 = "INSERT INTO
xero_invoices (ContactName, Description)
VALUES (:ContactName, :Description)";
$st3 = $conn3->prepare ( $sql3 );
$st3->bindValue( ":ContactName", $this->ContactName, PDO::PARAM_STR );
$st3->bindValue( ":Description", $desc, PDO::PARAM_STR );
$st3->execute();
$this->InvoiceNumber = $conn3->lastInsertId();
$conn3 = null;
}
This was my first attempt but gathered that the connection can only be used once then exits, so I tried an iteration but again I learnt that you can't do that with the PDO statement.
$i = 3;
foreach($detailsinvoice as $desc){
$conn[$i] = new PDO( DB_DSN, DB_USERNAME, DB_PASSWORD );
$sql[$i] = "INSERT INTO
xero_invoices (ContactName, Description)
VALUES (:ContactName, :Description)";
$st[$i] = $conn[$i]->prepare ( $sql[$i] );
$st[$i]->bindValue( ":ContactName", $this->ContactName, PDO::PARAM_STR );
$st[$i]->bindValue( ":Description", $desc, PDO::PARAM_STR );
$st[$i]->execute();
$this->InvoiceNumber = $conn[$i]->lastInsertId();
$conn[$i] = null;
$i++;
}
detailsinvoice is the array and the ContactName will be the same each time (the Contactname works just need to figure out looping the array)
I would appreciate if someone could point me in the right direction.

Answer 1

Feature of prepared statements is that you can prepare a statement once and then execute it multiple times, so your code can be rewritten as:
// Create a connection
$conn = new PDO( DB_DSN, DB_USERNAME, DB_PASSWORD );
$sql = "INSERT INTO
xero_invoices (ContactName, Description)
VALUES (:ContactName, :Description)";
// Create a statement
$st = $conn->prepare ($sql);
foreach ($detailsinvoice as $desc) {
// bind values and execute statement in a loop:
$st->bindValue( ":ContactName", $this->ContactName, PDO::PARAM_STR );
$st->bindValue( ":Description", $desc, PDO::PARAM_STR );
$st->execute();
$this->InvoiceNumber = $conn->lastInsertId();
}
// this is optional
$conn = null;

Answer 2

I have no idea where you got the idea a connection can only be used once from. You should connect only once in a script. Then as long as you store and pass around the $conn variable to any functions you may use (Scope of course is relevant here) you can use it as many times as you like.
// connect ONCE per script
$conn = new PDO( DB_DSN, DB_USERNAME, DB_PASSWORD );
// write the query once
$sql = "INSERT INTO xero_invoices (ContactName, Description)
VALUES (:ContactName, :Description)";
// and prepare it once.
$st = $conn->prepare ( $sql );
// now loop over the array of parameters any number of times you like
foreach($detailsinvoice as $desc){
$st->bindValue( ":ContactName", $this->ContactName, PDO::PARAM_STR );
$st->bindValue( ":Description", $desc, PDO::PARAM_STR );
$st->execute();
// this line looks wrong, as $this->InvoiceNumber will get overwritten
// each time round the loop
//$this->InvoiceNumber = $conn->lastInsertId();
// maybe you ment this, so at least you would have them all????
$this->InvoiceNumber[] = $conn->lastInsertId();
// or I have to assume you are going to add another query HERE
// that will use that ID
}
The concept of a prepared statement is that it is passed to the database, compiled, optimised and saved in the database almost like a stored proceedure.
Once prepared it can be used again and again. All you do is put new values into your parameters each time you execute it.