Uncaught Error: Class 'PHPMailer' not found

Question

I know there are many threads about this already but I can't make it work and I've already tried everything! There is no autoload.php on the phpmailer download and I'm stuck.

Please help, this error "class 'phpmailer' not found" keeps appearing even though I've already linked the required files. Xampp is running. All mailer files are inside folder PHPMailer (which contains folder src/ and inside it there are those 5 files I've linked). Thanks in advance!

<!--Contact Starts-->
        <div class="container contactform center">
            <h2 class="text-center  wowload fadeInUp"></h2>
            <div class="row wowload fadeInLeftBig">      
                  <div class="col-sm-6 col-sm-offset-3 col-xs-12">
                  <form method="post" action="index.php">
                    <input type="text" placeholder="Nombre" name="nombre" required>
                    <input type="email" placeholder="Email" name="email" required>
                    <input type="text" placeholder="Móvil" name="movil" required>
                    <textarea rows="5" placeholder="Mensaje" name="mensaje" required></textarea>
                    <button class="btn btn-danger" type="submit" name="sendBtn"><i class="fa fa-paper-plane"></i> Send</button>
                  </form>
                  </div>
            </div>
        </div>
    </div>
    <!--Contact Ends-->

<?php

if(isset($_POST["sendBtn"])){
    require "PHPMailer/src/PHPMailer.php";
    require "PHPMailer/src/OAuth.php";
    require "PHPMailer/src/SMTP.php";
    require "PHPMailer/src/POP3.php";
    require "PHPMailer/src/Exception.php";

    //Create a new PHPMailer instance

    $mail = new PHPMailer();

    //Tell PHPMailer to use SMTP

    $mail->isSMTP();


    //Enable SMTP debugging

    // 0 = off (for production use)

    // 1 = client messages

    // 2 = client and server messages

    $mail->SMTPDebug = 2;



    //Set the hostname of the mail server

    $mail->Host = 'smtp.gmail.com';

    // use

    // $mail->Host = gethostbyname('smtp.gmail.com');

    // if your network does not support SMTP over IPv6

    //Set the SMTP port number - 587 for authenticated TLS, a.k.a. RFC4409 SMTP submission

    $mail->Port = 587;

    //Set the encryption system to use - ssl (deprecated) or tls

    $mail->SMTPSecure = 'tls';

    //Whether to use SMTP authentication

    $mail->SMTPAuth = true;

    //Username to use for SMTP authentication - use full email address for gmail

    $mail->Username = "xxx@gmail.com";

    //Password to use for SMTP authentication

    $mail->Password = "xxxxxx";

    //Set who the message is to be sent from

    $mail->setFrom($_POST["email"], $_POST["nombre"]);

    //Set who the message is to be sent to

    $mail->addAddress('xxx@gmail.com', 'John Doe');

    //Set the subject line

    $mail->Subject = 'PHPMailer GMail SMTP test';

    //Read an HTML message body from an external file, convert referenced images to embedded,

    //convert HTML into a basic plain-text alternative body

    $mail->msgHTML(file_get_contents('contents.html'), dirname(__FILE__));



    //Replace the plain text body with one created manually

    $mail->AltBody = $_POST["mensaje"] . '<br><p Móvil: '.$_POST["movil"].'</p>';


    //send the message, check for errors

    if (!$mail->send()) {

        echo "Mailer Error: " . $mail->ErrorInfo;

    } else {

        echo "Message sent!";

    }
}

Answer 1

Method 1:
instead of this :

 //Create a new PHPMailer instance
$mail = new PHPMailer();

use this:

 //Create a new PHPMailer instance
$mail = new PHPMailer\PHPMailer\PHPMailer();

Edit on 2022-09-03
Method 2: (correct way)
as @Synchro said in comments, you can use the namespace in your script file instead of full namespace/class call:

// add namespace in top of your script
use PHPMailer\PHPMailer\PHPMailer;
// then call specify the class with this : 
$mail = new PHPMailer();