Change foreach $key variable inside the foreach loop - php

Question

Looking for a way to change $$key to something like $$key_errorso the variable will look something like: $name_error outside the foreach loop.
Here is what I have so far:
foreach ($_POST as $key => $value) {
$$key = strip_tags(mysqli_real_escape_string($mysqli, $value));
if (empty($value)) {
// change variable below to something like $$key_error ($$name_error)
$$key = 'is-invalid';
} else {
$$key = "value='$value'";
}
}
When an input is empty the user will return to the registration form, the input that is empty will have red bootstrap borders. When a field is not empty, the value will still be there so they do not have to do it all over.
<input type="text" name="name" class="form-control form-control-lg <?=$name?>" style="text-align:center;" placeholder="Voor- en achternaam" <?=$name?>>
I hope it all makes sense :)

Answer 1

Use arrays.
$errors = [];
$values = [];
foreach ($_POST as $key => $value) {
// validation check for $value
if (/*validation check fails*/) {
$errors[$key] = 'error message specific to this field';
} else {
$values[$key] = htmlspecialchars($value);
}
}
Then in your form, check for the array key matching your control name.
<input type="text" name="example"
class="<?= isset($errors['example']) ? 'is-invalid' : '' ?> other classes"
value="<?= $values['example'] ?? '' ?>">
You can also output the specific error message if you want to.
<div class="error"><?= $errors['example'] ?? '' ?></div>