Transmitir o número do botão de quantidade para outra página

<script type="text/javascript">

   function add( name ) { 

      document.getElementById( name ).value ++; 

   } 

   function substract( name ) { 

      if ( document.getElementById( name ).value > 0 )

      document.getElementById( name ).value --; 

   } 

 

   function isNumberKey(evt) 

   { 

      var charCode = (evt.which) ? evt.which : event.keyCode 

      if (charCode > 31 && (charCode < 48 || charCode > 57)) 

      return false; 

 

      return true; 

      } 

</script> 

 

<form> 

<input type="text" value="1" id="quantity" size="2" maxlength="4" onkeypress="return isNumberKey(event);">

<a onClick="add(‘quantity’);" >plus</a>

<a onClick="substract(‘quantity’);"> minus</a>

</form>

function add( name ) {

    if (document.getElementById( name ).value < <?php echo intval($stock); ?>) {

        document.getElementById( name ).value ++; 

    }

}

<form action="basket.php" method="get">

   <input type="hidden" name="action" value="add" />

   <input type="hidden" name="r" value="<?php echo htmlspecialchars($ref); ?>" />

   <input type="hidden" name="l" value="<?php echo htmlspecialchars($wording); ?>" />

   <input type="hidden" name="p" value="<?php echo htmlspecialchars($price); ?>" />



   <input type="text" value="1" id="quantity" name="yourquantityattribute" size="2" maxlength="4" onkeypress="return isNumberKey(event);">

   <a onClick="add(‘quantity’);" >plus</a>

   <a onClick="substract(‘quantity’);"> minus</a>



   <button type="submit"><img src="images/product-details/caddieshop.png"></button>

</form>