PHP如何使URL像product.php？id = 1

I am doing a simple php cart. Basically is for learning purpose and I am trying to search solution for my question. However, i am not sure what is the keyword for my question. Hence, I post it here.

echo "<p>Product A | <a href='product.php?id=a'>Add to Cart</a></p>";
echo "<p>Product B | <a href='product.php?id=b'>Add to Cart</a></p>";
echo "<p>Product C | <a href='product.php?id=c'>Add to Cart</a></p>";

Basically, every product shares the same landing page -> product.php just like normal shopping cart. So when user clicks product A "Add to Cart", it will land on produt.php?id=a , if product B, then will be produt.php?id=b . My questions is how to make the url sth like I mentioned?

Please refer to a screenshot.

Since the id parameter is in the url it is called a GET parameter. You can access to GET parameters using the global variable $_GET.

In product.php you should have something like:

if(isset($_GET['id'])){
    $id = $_GET['id'];
    if($id=='a'){
        // do something
    }
    else if($id=='b'){
        // do something else
    }   
}

if(isset($_GET['id'])){
    if(is_numeric($_GET['id']))
    {
       $id = $_GET['id'];
        if($id=='a')
       {

       }
       else if($id=='b')
      {
        // do something else
      }else
     {
       echo "product does not exists";
     }

   }
   else{
   echo "product does not exists";
   }



}else
{
   echo "product does not exists";     
}

Try the following:

// Show all products
$q = mysqli_query( $con, "SELECT `id` FROM `products`" );
if( mysqli_num_rows( $q ) > 0 ) { // Check if there are results
    while( $row = mysqli_fetch_assoc( $q ) ) {
        echo '<p>Product A | <a href="product.php?id='.$row['id'].'">Add to Cart</a></p>';
    }
}

In product.php

function productExists( $id ) {
    if( !empty( $id ) ) {
        $q = mysqli_query( $con, "SELECT `id` FROM `products` WHERE `id` = $id");

        if( mysqli_num_rows( $q ) > 0 ) {
            return true;
        } else {
            return false;
        }
    } else {
        return false;
    }
}

function productData( $id ) {
    if( !empty( $id ) ) {
        $q = mysqli_query( $con, "SELECT `id`, `product_name`, `product_price`, `product_quantity`, `product_image` FROM `products` WHERE `id` = $id");

        if( mysqli_num_rows( $q ) > 0 ) {
            $data = array(); // Store data
            while( $row = mysqli_fetch_assoc( $q ) ) {
                $data[] = $row;
            }

            if( !empty( $data ) ) { // Make sure all data is gathered before proceeding
                return $data;
            } else {
                return false;
            }
        } else {
            return false;
        }
    } else {
        return false;
    }
}

if( !empty( $_GET['id'] ) ) { // empty does the same as isset() but also checks if the value is not empty
    $id = (int)mysqli_real_escape_string( $con, $_GET['id'] );

    if( productExists( $id ) ) {
        $data = productData( $id );

        echo 'Product: '.$data['product_name']; // Etc.
    } else {
        echo 'Product doesn\'t exists';
    }
}

When adjusting some of the code you're also able to get the other columns