Record data as array in txt file - php

Question

I need to create very simple register/login system in PHP. User details must be stored in array in txt file. For some reasons even when PHP not show any error details are not saved to txt file. Any hint?
$fullname='';
$email ='';
$username ='';
$password = '';
$error = '';
$form_is_submitted = false;
$errors_detected = false;
$clean = array();
$errors = array();
if (isset($_POST['submit'])) {
$form_is_submitted = true;
if (ctype_alnum ($_POST['fullname'])) {
$clean['fullname'] = $_POST['fullname'];
} else {
$errors_detected = true;
$errors[] = 'Please enter your Full Name!';
}
if (ctype_alnum ($_POST['email'])) {
$clean['email'] = $_POST['email'];
} else {
$errors_detected = true;
$errors[] = 'You have enter an invalid e-mail address. Please, try again!';
}
if (ctype_alnum ($_POST['username'])) {
$clean['username'] = $_POST['username'];
} else {
$errors_detected = true;
$errors[] = 'Please enter your user name!';
if (ctype_alnum ($_POST['password'])) {
$clean['password'] = $_POST['password'];
} else {
$errors_detected = true;
$errors[] = 'Please enter a valid password!';
}
}
if ($form_is_submitted === true
&& $errors_detected === false) {
$fp = fopen('filewriting.txt', 'w');
fwrite($fp, print_r($clean, TRUE));
fclose($fp);
} else {
echo $errors;
}

Answer 1

There are a few things wrong with your code.
There is a missing brace for
if (isset($_POST['submit'])) {$form_is_submitted = true;
so it needs to read as
if (isset($_POST['submit'])) {
$form_is_submitted = true;
}
You are using ctype_alnum so when it comes to an email address, the # and the dot do not count as alpha-numerical characters a-z A-Z 0-9; either remove it if(ctype_alnum ($_POST['email'])) which proved to be successful in testing this.
You can also use another function such as FILTER_VALIDATE_EMAIL
I quote from the PHP manual:
Return Values
Returns TRUE if every character in text is either a letter or a digit, FALSE otherwise.
This block has a misplaced brace
if (ctype_alnum ($_POST['username'])) {
$clean['username'] = $_POST['username'];
} else {
$errors_detected = true;
$errors[] = 'Please enter your user name!';
if (ctype_alnum ($_POST['password'])) {
$clean['password'] = $_POST['password'];
} else {
$errors_detected = true;
$errors[] = 'Please enter a valid password!';
}
}
Which should read as
if (ctype_alnum ($_POST['username'])) {
$clean['username'] = $_POST['username'];
} else {
$errors_detected = true;
$errors[] = 'Please enter your user name!';
} // was missing
if (ctype_alnum ($_POST['password'])) {
$clean['password'] = $_POST['password'];
} else {
$errors_detected = true;
$errors[] = 'Please enter a valid password!';
}
// } // was misplaced - commented out to show you
otherwise it would not have written the password (as part of the array) to file.
Plus this $error = ''; should "probably" read as $errors = ''; but that didn't stop it from writing the data to file.
As for the Array message, remove the square brackets [] from all instances of $errors[]

Answer 2

I think
fwrite($fp, print_r($clean, TRUE));
should be
fwrite($fp, $clean, TRUE);
or
file_put_contents($fp, $clean);