Inserting multiple rows into mysql db using php - php

Question

Am having a problem inserting multiple rows of data into a table at once. The following is what i have.When i click on submit, only the last row is inserted with only the first digit of quantity. please help.
html form:
<form method="post" action="insert.php">
<p><input type="text" id="product_id" name="product_id[]"/>
<input type="text" id="quantity" name="quantity[]"/></p>
<p><input type="text" id="product_id" name="product_id[]"/>
<input type="text" id="quantity" name="quantity[]"/></p>
<p><input type="text" id="product_id" name="product_id[]"/>
<input type="text" id="quantity" name="quantity[]"/></p>
<input type="submit" name="submit" value="submit"/>
</form>
insert.php page:
<?php
include 'config/auth.php';//database connection
if(isset($_POST['submit'])){
$product = mysqli_real_escape_string($dbc, $_POST['product_id']);
$quantity = mysqli_real_escape_string($dbc, $_POST['quantity']);
$count = sizeof($product);
for ($i=0; $i < $count; $i++) {
$Inproduct = $product[$i];
$Inquantity = $quantity[$i];
$query = "INSERT INTO sales (product_id, quantity) VALUES ('$Inproduct','$Inquantity')";
$results = mysqli_query($dbc, $query);
}
if ($results) {
echo 'Success';
}
}
?>

Answer 1

the following code worked... thanks #kmdm
$product = $_POST['product_id'];
$quantity = $_POST['quantity'];
$count = sizeof($product);
for ($i=0; $i < $count; $i++) {
$Inproduct = mysqli_real_escape_string($dbc, $product[$i]);
$Inquantity = mysqli_real_escape_string($dbc, $quantity[$i]);
$query = "INSERT INTO sales (product_id, quantity) VALUES ('$Inproduct','$Inquantity')";
$results = mysqli_query($dbc, $query);
}