PHP Custom Email using PHPMailer

I am designing an email feature for a client, the main requirements is to keep user on same page if user has some errors in email, the errors should be shown on the same page.

For that I have created this HTML (PHP)

<?php

session_start();

require_once '../helpers/security.php';

$errors = isset($_SESSION['errors']) ? $_SESSION['errors'] : [];
$fields = isset($_SESSION['fields']) ? $_SESSION['fields'] : [];

?>
<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <title>PHPmailer</title>
        <link rel="stylesheet" href="../css/style.css">
    </head>
    <body>
        <div class="contact">
            <?php if(!empty($errors)): ?>
                <div class="panel">
                    <ul>
                        <li><?php echo implode('</li><li>', $errors); ?></li>
                    </ul>
                </div>
            <?php endif; ?>
            <form action="contact.php" method="POST">
                <label>
                    Your Name*
                    <input type="text" name="name" autocomplete="off"<?php echo isset($fields['name']) ? 'value="'.e($fields['name']).'"' : '' ?>>
                </label>
                <label>
                    Your Email*
                    <input type="text" name="email" autocomplete="off"<?php echo isset($fields['email']) ? 'value="'.e($fields['email']).'"' : '' ?>>
                </label>
                <label>
                    Your Message*
                    <textarea name="message" rows="8"><?php echo isset($fields['message']) ? e($fields['message']) : '' ?></textarea>
                </label>
                <input type="submit" value="Send">
                <p class="muted">* means a required field</p>
            </form>
        </div>
    </body>
</html>
<?php

unset($_SESSION['errors']);
unset($_SESSION['fields']);

?>

And this is my PHP code

<?php

session_start();

require_once '../phpmailer/PHPMailerAutoload.php';

$errors = [];

if(isset($_POST['name'], $_POST['email'], $_POST['message'])){
    $fields = [
        'name' => $_POST['name'],
        'email' => $_POST['email'],
        'message' => $_POST['message']
    ];
    
    foreach($fields as $field => $data){
        if(empty($data)){
            $errors[] = 'The '.$field.' field is required';
        }
    }
    
    if(empty($errors)){
        $m= new PHPMailer;
        $m->isSMTP();
        $m->SMTPAuth = true;
        
        /*$m->SMTPDebug = 1; */
        
        $m->Host = 'smtp.gmail.com';
        $m->Username = 'mymail@gmail.com';
        $m->Password = 'mypass';
        $m->SMTPSecure = 'ssl';
        $m->Port = 465;
        
        $m->isHTML();
        
        $m->Subject = 'Contact form submitted';
        $m->Body = 'From: '.$fields['name'].' ('.$fields['email'].')<p>'.$fields['message'].'</p>';
        
        $m->FromName = 'Contact';
        
        /*$m->AddReplyTo($fields['email'], $fields['name']);*/
        
        $m->AddAddress('mymail@gmail.com', 'My Name');
        
        if($m->send()){
            header('Location: http://facebook.com');
            die();
        } 
        else {
            $errors[]= 'Error';
        }
    }
} 
else{
    $errors[] = 'something went wrong';
}

$_SESSION['errors'] = $errors;
$_SESSION['fields'] = $fields;

header('Location: http://google.com');

?>

I have added additional security code

<?php

function e($string){
    return htmlentities ($string, ENT_QUOTES, 'UTF-8', false);
}

?>

I have tried this code but it won't work it gives me "500" server error on the index page as well as contact.php page I have checked with ";" and other general PHP errors I have checked just by echoing the variables in PHP (PHP works :P )

On the index page if I remove

? $_SESSION['errors'] : [];
? $_SESSION['fields'] : [];

From

$errors = isset($_SESSION['errors']) ? $_SESSION['errors'] : [];
$fields = isset($_SESSION['fields']) ? $_SESSION['fields'] : [];

The index page shows form HTML but when I submit the form I get 500 server error on contact.php

Please help me out this code

Solution

To get rid of the 500 Internal server error:

A) Place this snippet right after

ini_set('display_errors', 'on');
error_reporting(-1);

B) If A is not working, try creating a .htaccess file in the web-root directory with this in it:

php_value error_reporting -1
php_flag display_errors on

C) If B is not working, then your apache\httpd server does not have AllowOverride enabled. You then should change the php.ini (same as B)

(one should never do all the above in production. Only use this while developing)

Now you should be able to see the error, which will be probably that [] is not supported by your PHP version. Try changing all [] to array().