How to get data from an array of check boxes

The HTML that stores three related check boxes in an array

      
      <input type="checkbox" id="pep" name="top[]" checked />Pepperoni<br />
      <input type="checkbox" id="msh" name="top[]" checked />Mushrooms<br />
      <input type="checkbox" id="olv" name="top[]" checked />Olives<br />

PHP that accesses the array and its values

      <php
      $toppings = filter_input(INPUT_POST, 'top', 
                               FILTER_SANITIZE_SPECIAL_CHARS, FILTER_REQUIRE_ARRAY);
      if ($toppings !== NULL) { 
        $top1 = $toppings[0]; // $top1 is pep
        $top2 = $toppings[1]; // $top2 is olv
        $top3 = $toppings[2]; // $top3 is not set – throws an error
      }
      ?>

PHP that uses a loop to process the array

      
      <php
      $toppings = filter_input(INPUT_POST, 'top', 
                               FILTER_SANITIZE_SPECIAL_CHARS, FILTER_REQUIRE_ARRAY);
      if ($toppings !== NULL) { 
        echo("<p>");
        foreach($toppings as $key => $value) {
          echo("$key = $value<br />\n");
        }
        echo("</p>\n");
      } else {
        echo("No toppings selected.</p>\n");
      }
      ?>

If a check box name ends with [], PHP adds the check box to an array that's nested in the $_GET or $_POST array. This allows multiple values to be submitted with the same name.
If none of the check boxes in an array of check boxes are selected, the array won't be set in the $_GET or $_POST array.
If you're going to use the checkbox values, you should use a PHP function like the filter_input() function to get the values of the array and to make sure they are safe. To do that, you can use filters like the ones shown on this page.

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