如何在PHP中将多个参数传递给URL

Question

I have a problem in passing 2 parameters via URL I don't know how, so I wrote this:

<form method="get" >
   <b>Enter the Quantity you want:</b>
   <input type="text" name="quantity">
</form>

<br><br>

<a href='./shopping-cart.php?part_id="<?php echo $_GET['part_id']; ?>"&quantity="<?php echo $_GET['quantity']; ?>"'>
   <img src="add_to_shopping_cart.png">
</a>

$_GET['part_id'] this var from another URL and I want to pass it again and $_GET['quantity'] quantity from form.

Answer 1

You must use urlencode function for your parameters, and don't use the double quotes:

<a href='./shopping-cart.php?part_id=<?php echo urlencode($_GET['part_id']); ?>&quantity=<?php echo urlencode($_GET['quantity']); ?>'>

Even though, I suggest you to avoid long urls and use POST with hidden fields.

Answer 2

There's a few errors that I can see.

You can't use $_GET['quantity'] if the user is entering it in without reloading the page (Remember, PHP is not client-side). Thus, I suggest using JavaScript for that.

Javascript:

function buildUrl(a) {
   var qty = document.getElementById("qty").value; 
   a.href = "./shopping-cart.php?part_id="+<?php echo $_GET['part_id']; ?>
   +"&quantity="+qty;
}

As you no longer need to get a PHP variable from the current page, the form is obsolete and a simple link will do.

HTML:

<b>Enter the Quantity you want:</b>
<input type="text" name="quantity">
<a href='#' onclick="buildUrl(this);"> //onclick attribute triggers the JavaScript
    <img src="add_to_shopping_cart.png">
</a> 

Answer 3

You get this notice Undefined index: quantity cause you are trying to access an undefined variable. If your page url is something like page_name.php?quantity=5 then $_GET['quantity] is set, otherwise it isn't.

You should check if the $_GET variable exist. If so, use @user4035 answer to print the url.

if(isset($_GET['quantity']))
{ 
    //html code,the url
    //echo $_GET['quantity']
}