Validate PHP variable via Javascript

Question

Im looking to pass one variable from my PHP code to my Javascript code to validate a figure. I'm creating a shopping cart scenario whereby i have a variable 'in_stock' which specifies the amount of stock available for a product. If I enter an amount that is greater than the 'in_stock' available i need an error to be thrown. This is currently what I have:

Java Script

   <script language="javascript">
  function numCheck() 
  {
        var enteredChar = document.getElementById('add_value').value;
        var stockavailable ="<?php echo $stock?>";

    //To check if a non-numerical value is entered
    if (isNaN(enteredChar)) 
    {
        alert("Not a Number!");
        return false;
    }
    //To check if the input is empty
    if (enteredChar=="")
    {
        alert("Empty!");
        return false;
    }
    //To check if the amount entered is not greater than the amount in stock
 if (enteredChar > stockavailable)
    {
        alert("Not enough in stock");
        return false;
    }

 }  
   </script>

This is all occurring whilst my PHP has called the database and returned the value on the screen. As follows:

PHP

$product_id =(int)$_GET['product_id'];

$username = "potiro";
$password = "pcXZb(kL";
$hostname = "rerun";

//connection to the database
$dbhandle = mysql_connect($hostname, $username, $password)
 or die("Unable to connect to MySQL");


//select a database to work with
$selected = mysql_select_db("poti",$dbhandle)
  or die("Could not select examples");

//execute the SQL query and return records
$result = mysql_query("SELECT * FROM products where product_id=$product_id");

echo '<form name="form1">';
echo '<table class="Grocery-table">'; 

while($row = mysql_fetch_array($result))
{

$stock =$row['in_stock'];
$product_id = $row['product_id'];

  echo "<tr><td><b>Product ID</b></td>"; 
  echo "<td>";  
  echo $product_id;
  echo "</td></tr>";
  echo "<tr><td><b>Product Name</b></td>";
  echo "<td>";
  echo $row['product_name'];
  echo "</td></tr>"; 
   echo "<tr><td><b>Unit Price</b></td>";
  echo "<td>";
  echo $stock;
  echo "</td></tr>"; 
  echo "<tr><td><b>Unit Quantity</b></td>";
  echo "<td>";
  echo $row['unit_quantity'];
  echo "</td></tr>"; 
  echo "<tr><td><b>In Stock</b></td>";
  echo "<td>";
  echo $row['in_stock'];
  echo "</td></tr>";
  echo '<tr><td><b>Add</b></td><td><Input type="text" id="add_value" name="cart"></input></td></tr>';
  echo '<tr><td></td><td><input type="submit" value="Submit" onclick="return numCheck()"></td></tr>';
 }
echo "</table>"; 
echo "</form>";

mysql_close($dbhandle);
?>

variable $stock = $row['in_stock']; - whatever the value is in that row — JavaHater
– JavaHater, Commented Apr 3, 2015 at 6:01

Ghostman · Accepted Answer · 2015-04-03 06:29:24Z

2

add your stock value to a hidden input value stock_value

 echo '<tr><td><b>Add</b></td><td><Input type="text" id="add_value" name="cart"  ></input><Input type="hidden" id="stock_value" name="stock_value"  value="'.trim($stock).'"></input></td></tr>';
 echo '<tr><td></td><td><input type="submit" value="Submit" onclick="return numCheck()"></td></tr>';

in javascript

<script language="javascript">
  function numCheck() 
  {
        var enteredChar = document.getElementById('add_value').value;
        var stockavailable =document.getElementById('stock_value').value;

edited Apr 3, 2015 at 6:29

answered Apr 3, 2015 at 5:22

Ghostman

6,1129 gold badges36 silver badges53 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

JavaHater Over a year ago

it seems when i add the hidden input field the "value" in the form for the Add is "<?php echo $stock; ?>" instead of blank where im supposed to place a value there.

Ghostman Over a year ago

i didn't get you... can u brief more

JavaHater Over a year ago

it is still not validating against the stock_value .. is there something in my PHP that i may need to change?

Ghostman Over a year ago

is the value been sent to javascript through id

JavaHater Over a year ago

Let us continue this discussion in chat.

Collectives™ on Stack Overflow

Validate PHP variable via Javascript

1 Answer 1

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related