PHP `use` import namespace causes page to crash - php

Question

PHPMailer is working fine in a test script on it's own bare bones. However, it is crashing and not reporting an any errors on another page. I have isolated the problem to the following lines of code:
use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\Exception;
When I leave these lines out I get the PHP error:
Fatal error: Uncaught Error: Class 'PHPMailer' not found in /path/to/file.php:166 Stack trace: #0 {main} thrown in /path/to/file.php on line 166
When I include these lines (which I believe I need to in order to use the namespace of the imported classes) I simply get a blank white screen. Error reporting is turned on at the top of the page as follows:
error_reporting(E_ALL);
ini_set('display_errors', 1);
However, no error reports on the page.
The rest of the class files are imported as below and the path is correct as they report no errors unless I change the path.
require '../../../wp-content/plugins/PHPMailer/Exception.php';
require '../../../wp-content/plugins/PHPMailer/PHPMailer.php';
require '../../../wp-content/plugins/PHPMailer/SMTP.php';
I looked for information about use on the PHP website, however there was nothing listed when I searched (http://ca3.php.net/manual-lookup.php?pattern=use&scope=quickref).
Here is the full code in the file.php. I know there are other issues such as data input sanitization, etc, but I am refactoring someone else's code:
<?php
error_reporting(E_ALL);
ini_set('display_errors', 1);
var_dump($_POST);
// PayPal Config Constants
require "../../../mail-config.php";
require "../../../keys-config.php";
/** Send HTTP POST Request for PayPal Payment */
function PPHttpPost($methodName_, $nvpStr_) {
// Get the environment set in the keys-config.php file
$environment = PAYPAL_ENVIRONMENT;
// Use the keys and endpoint for the environment
if("sandbox" === $environment || "beta-sandbox" === $environment) {
// Set the API URL
$API_Endpoint = PAYPAL_API_ENDPOINT_SANDBOX;
// Set up your API credentials, PayPal end point, and API version.
$API_UserName = urlencode(PAYPAL_API_USERNAME_SANDBOX);
$API_Password = urlencode(PAYPAL_API_PASSWORD_SANDBOX);
$API_Signature = urlencode(PAYPAL_API_SIGNATURE_SANDBOX);
} else {
// Set the API URL
$API_Endpoint = PAYPAL_API_ENDPOINT;
// Set up your API credentials, PayPal end point, and API version.
$API_UserName = urlencode(PAYPAL_API_USERNAME);
$API_Password = urlencode(PAYPAL_API_PASSWORD);
$API_Signature = urlencode(PAYPAL_API_SIGNATURE);
}
// Set the version
$version = urlencode('51.0');
// Set the curl parameters.
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $API_Endpoint);
curl_setopt($ch, CURLOPT_VERBOSE, 1);
// Turn off the server and peer verification (TrustManager Concept).
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, FALSE);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_POST, 1);
// Set the API operation, version, and API signature in the request.
$nvpreq = "METHOD=$methodName_&VERSION=$version&PWD=$API_Password&USER=$API_UserName&SIGNATURE=$API_Signature$nvpStr_";
// Set the request as a POST FIELD for curl.
curl_setopt($ch, CURLOPT_POSTFIELDS, $nvpreq);
// Get response from the server.
$httpResponse = curl_exec($ch);
// If the method failed
if(!$httpResponse) {
exit("$methodName_ failed: ".curl_error($ch).'('.curl_errno($ch).')');
}
// Extract the response details.
$httpResponseAr = explode("&", $httpResponse);
$httpParsedResponseAr = array();
foreach ($httpResponseAr as $i => $value) {
$tmpAr = explode("=", $value);
if(sizeof($tmpAr) > 1) {
$httpParsedResponseAr[$tmpAr[0]] = $tmpAr[1];
}
}
// If data in response is invalid
if((0 == sizeof($httpParsedResponseAr)) || !array_key_exists('ACK', $httpParsedResponseAr)) {
exit("Invalid HTTP Response for POST request($nvpreq) to $API_Endpoint.");
}
// Return the http response
return $httpParsedResponseAr;
}
// Prepare PayPal Payment Request
// Set request-specific fields.
// 'Authorization' or 'Sale'
$paymentType = urlencode('Sale');
// Name Details
$firstName = urlencode($_POST['firstname']);
$lastName = urlencode($_POST['lastname']);
// Credit Card details
$creditCardType = urlencode($_POST['customer_credit_card_type']);
$creditCardNumber = urlencode($_POST['cardnum']);
$expDateMonth = $_POST['cc_expiration_month'];
// Month must be padded with leading zero
$padDateMonth = urlencode(str_pad($expDateMonth, 2, '0', STR_PAD_LEFT));
$expDateYear = urlencode($_POST['cc_expiration_year']);
$cv = urlencode($_POST['cv']);
// Address Details
$address1 = urlencode($_POST['streetaddy']);
$city = urlencode($_POST['city']);
$state = urlencode($_POST['province']);
$postal_code = urlencode($_POST['postalcode']);
// US or other valid country code
$country = urlencode($_POST['country']);
$price = urlencode($_POST['price']);
// or other currency ('GBP', 'EUR', 'JPY', 'CAD', 'AUD')
$currencyID = urlencode('CAD');
// Add request-specific fields to the request string.
$nvpStr = "&PAYMENTACTION=$paymentType&AMT=$price&CREDITCARDTYPE=$creditCardType&ACCT=$creditCardNumber".
"&EXPDATE=$padDateMonth$expDateYear&CVV2=$cv&FIRSTNAME=$firstName&LASTNAME=$lastName".
"&STREET=$address1&CITY=$city&STATE=$state&ZIP=$postal_code&COUNTRYCODE=$country&CURRENCYCODE=$currencyID";
// Execute the API operation; see the PPHttpPost function above.
$httpParsedResponseAr = PPHttpPost('DoDirectPayment', $nvpStr);
if("SUCCESS" == strtoupper($httpParsedResponseAr["ACK"]) || "SUCCESSWITHWARNING" == strtoupper($httpParsedResponseAr["ACK"])) {
//Below line is response code from original
//exit('Direct Payment Completed Successfully: '.print_r($httpParsedResponseAr, true));
// Require the PHPMailer classes
use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\Exception;
require '../../../wp-content/plugins/PHPMailer/Exception.php';
require '../../../wp-content/plugins/PHPMailer/PHPMailer.php';
require '../../../wp-content/plugins/PHPMailer/SMTP.php';
//FIELDS
$first_name = $_POST['firstname'];
$last_name = $_POST['lastname'];
$email_from = $_POST['email'];
$phone = $_POST['phone'];
$ad = $_POST['ad'];
$price = $_POST['price'];
$edition = $_POST['edition'];
$issues = $_POST['issues'];
$category = $_POST['category'];
$order_id = $_POST['order_id'];
$email_message = "A Classified Ad has been purchased from the Speaker website. Details of the ad are below.\n\n";
// Filter the string
function clean_string($string) {
$bad = array("content-type","bcc:","to:","cc:","href");
return str_replace($bad,"",$string);
$string = filter_var($string, FILTER_SANITIZE_STRING, FILTER_FLAG_STRIP_LOW);
}
// Build the Email message body contents
$email_message .= "<b>Order ID:</b> ".clean_string($order_id)."<br>";
$email_message .= "<b>First Name:</b> ".clean_string($first_name)."<br>";
$email_message .= "<b>Last Name:</b> ".clean_string($last_name)."<br>";
$email_message .= "<b>Email:</b> ".clean_string($email_from)."<br>";
$email_message .= "<b>Telephone:</b> ".clean_string($phone)."<br>";
$email_message .= "<b>Category:</b> ".clean_string($category)."<br>";
$email_message .= "<b>Ad Text:</b> ".clean_string($ad)."<br>";
$email_message .= "<b>Edition:</b> ".clean_string($edition)."<br>";
$email_message .= "<b>Number of Issues:</b> ".clean_string($issues)."<br>";
$email_message .= "<b>Price:</b> ".clean_string($price)."<br>";
// Set up the email to be sent
$mail = new PHPMailer(); // create a new object
$mail->IsSMTP(); // enable SMTP
$mail->SMTPDebug = 0;
$mail->SMTPAuth = true; // authentication enabled
$mail->SMTPSecure = 'ssl'; // secure transfer enabled REQUIRED for Gmail
$mail->Host = "smtp.gmail.com";
$mail->Port = 465; // or 587
$mail->IsHTML(true);
$mail->Username = SITE_EMAIL_SMTP_USERNAME;
$mail->Password = SITE_EMAIL_SMTP_PASSWORD;
$mail->SetFrom(SITE_EMAIL_FROM_ADRESS_LIST);
$mail->Subject = "Classified Ad Submission From The ".NEWSPAPER_NAME." Website";
$mail->Body = $email_message;
// Add all the company email addresses to the send list
foreach(PAYWALL_NOTIFICATION_EMAIL_ADDRESSES_ARRAY as $email_address){
$mail->AddAddress($email_address);
}
// Add the purchaser's email address to the send list
$mail->AddAddress($email_from);
// If mail fails to send
if(!$mail->Send()) {
//REDIRECT TO FAILED PAGE
header( 'Location: /order-not-completed' );
} else {
//REDIRECT TO SUCCESS PAGE
header( 'Location: /success' );
}
} else {
//Below line is response code for testing
exit('DoDirectPayment failed: ' . print_r($httpParsedResponseAr, true));
//REDIRECT TO FAILED PAGE
header( 'Location: /order-not-completed' );
}
?>

Answer 1

It will mean that your PHP version is too old. Namespaces and the use syntax were introduced in PHP 5.3, and that is already many years out of date.
PHPMailer 6.0.x requires at least PHP 5.5, so update your PHP, ideally to the latest version (currently 7.3).

Answer 2

Here is the page describing the use of PHP's use function to import namespaces: http://php.net/manual/en/language.namespaces.importing.php
Scoping rules for importing
The use keyword must be declared in the outermost scope of a file (the
global scope) or inside namespace declarations. This is because the
importing is done at compile time and not runtime, so it cannot be
block scoped. The following example will show an illegal use of the
use keyword:
namespace Languages;
function toGreenlandic() {
use Languages\Danish;
// ... }
Although the above code is not using the use statement in side a function, it is not at the top of the file and other functions were declared before the use statements. I tested the above code with after moving the use statements to the top of the file directly under the
In short: always put your use statements at the top of your PHP file and outside of the functions or classes.