Validation of data submitted by the form

Question

I am validating a form and I face a problem that I cannot solve. First, I make a foreach and check if there are any $_POST empty, if any, executes: $error[$key] = "*";. Then, below the input, I check if the user clicked on Submit and whether the variable $error[$key] was set, if yes, prints "*"; <br>, but nothing happens.

foreach:

foreach ($_POST as $key => $value) {
   if(empty($_POST[$value])) {
      $error[$key] = "*";
      $valida = false;
   }
}

input:

<input type="text" class="demoInputBox" name="firstName" value="<?php if(isset($_POST['firstName'])) echo $_POST['firstName']; ?>">
<?php if ($_SERVER['REQUEST_METHOD'] == 'POST' and isset($error['firstName'])) echo "<label style = 'color: #ff0000'>" . $error['firstName'] . "</label>"; ?>

Answer 1

How are you assigning the value of input for $key, replace the

if(empty($_POST[$value])) {
  ...
}

for

if(empty($_POST[$key])) {
  ...
}

Complete:

<?php
foreach ($_POST as $key => $value) {
    if(empty($_POST[$key])) {
        $error[$key] = "*";
        $valida = false;
    }
}
?>
<form method="post">
    <input type="text" class="demoInputBox" name="firstName" value="<?php if(isset($_POST['firstName'])) echo $_POST['firstName']; ?>">
    <?php if ($_SERVER['REQUEST_METHOD'] == 'POST' and isset($error['firstName'])) echo "<label style = 'color: #ff0000'>" . $error['firstName'] . "</label>"; ?>
    <input type="submit">
</form>