grabbing data from $_POST when you don't know what you need to grab in advance

This will make sense with an example:

You've got a recipe site, that tracks 3 datapoints:

• recipe name (salad, chowder, etc.)
• ingredients (tomato, potato, pork, etc.)
• ingredient volume (integers only, to keep our example simple)

On the first page of my Recipe Editor we have a form to list the required ingredients.

Recipe: salad
  REQUIRES
    __ tomato
    __ lettuce
    __ cheese
    __ schweddy balls

On the second page, we get a list of all required ingredients and input boxes to enter the required volumes:

Recipe: salad
Ingredient    Volume
 tomato         2
 lettuce        1
 cheese         1

(contrived, I know, but bear with me)

Now that second form's list of ingredients and <input ... /> boxes are generated dynamically from the database depending on the recipe chosen for editing.

Each ingredient has a numeric ID, so your volume input would look like:

<input type="text" name="17" value="" /> // how many tomatoes?

Once you SUBMIT, you need to process the $_POST array and upload all the ingredients and volumes -- but you (or at least I) don't know in advance what will be in that $_POST array because each recipe calls for differen开发者_如何学JAVAt ingredients == $_POST[???]

The super-kludge I thought of was putting all the ingredient IDs into a comma-separated string, stick that into a hidden input field, and the explode it during processing and use it as $_POST keys to pull out the values. This certainly works, but it makes me feel all dirty inside.

Is there a better approach to getting input values out of $_POST when you don't know your keys in advance?

The easiest way is to use foreach, since $_POST acts just like any other array:

foreach($_POST as $key => $value)
{
    switch($key)
    {
        case 17:
        // ...
    }
}

You can also check for the presence of specific keys using isset():

if(isset($_POST['17'])) {
    // ...
}

And for the record: there's nothing wrong with comma-separated input fields. The best solution is the one that works. :)

That's not an uncommon issue, and for the recipies the approach looks plausible. But there is an alternative approach, if you would be able to adapt the form generation logic:

<input type="number" name="volume[tomatos]" value="">

Or keep using IDs with name="volume[17]" or something alike.

Anyway I think this is easy to generate with AJAX/DHTML too, and PHP can deal better with an input array like $_GET["volume"][...] - which in some cases can also be more reliable than receiving an uncertain ID-list. (You would still need the foreach certainly.)

<input type="text" name="17" value="" />

Assuming your form method is POST...

foreach($_POST as $key => $value){
    echo "We need $value of item $key";
}

Should get you headed in the right direction.

foreach ($_POST as $key => $value){
    echo "This recipe includes $value of ingredient $key."
}

To get the list of ingredient IDs, extract it from the $_POST array:

$ingredientIDs = array_keys($_POST);