Question

I have page1.php that uses a form to send the following data:

<form action="page2.php" method="post">
<input type="text" name="f1">
<input type="text" name="f2">
<input type="text" name="f3">
<input type="text" name="f4">
<input type="submit" value="submit">
</form>

On page2.php, I do some basic validation so see that the form was actually submitted and that all data was entered:

<?php
if($_SERVER['REQUEST_METHOD'] != "POST" || empty($_POST["f1"]) || empty($_POST["f2"]) || empty($_POST["f3"]) || empty($_POST["f4"]))
{
    $missing_input = array();

    if (empty($_POST["f1"]))
    {
        $missing_input[] = "field1";
    }
    if (empty($_POST["f2"]))
    {
        $missing_input[] = "field2";
    }
    if (empty($_POST["f3"]))
    {
        $missing_input[] = "field3";
    }
    if (empty($_POST["f4"]))
    {
        $missing_input[] = "field4";
    }

    die("Error: " . implode(", ", $missing_input)");
}
?>

The problem is that the above feels very ugly and needs re-work when a new POST field is introduced in the page1.php form. How can I code this form validation better?

Answer 1

Store f1, f2, etc. in an array and use a for statement to iterate through the array.

Example:

if($_SERVER['REQUEST_METHOD'] != "POST")
    die("Error: Wrong method");
$fields = array("f1", "f2", "f3", "f4");
$field_names = array("field1", "field2", "field3", "field4");
$length = count($fields);
$missing_input = array();
for($i = 0; $i < $length; $i++)
    if(empty($_POST[$fields[$i]]))
        $missing_input[] = $field_names[$i];
if(!empty($missing_input))
    die("Error: " . implode(", ", $missing_input)");

Note: The above is untested.