Email Sends but console displays a 500 Error

I have some javascript that is triggered and runs this code:

async function sendWelcomeEmail(email) {
        return new Promise((resolve, reject) => {
            $.ajax({
                type: "POST",
                url: '/Emails/welcomeEmail.php',
                data: {
                    email: email
                },
                success: response => {
                    console.log(response);
                    resolve();
                }
            });
        })
    }

Which then runs the test file:

// Test the connection by sending a simple email
    try {
        $result = $SesClient->sendEmail([
            'Source' => 'sendingEmailAddress',
            'Destination' => [
                'ToAddresses' => ['testEmailAddress'],
            ],
            'Message' => [
                'Subject' => [
                    'Data' => 'Test Email',
                ],
                'Body' => [
                    'Text' => [
                        'Data' => 'This is a test email sent using AWS SES.',
                    ],
                ],
            ],
        ]);

        // If the request was successful, print the message ID
        echo "Email sent! Message ID: " . $result['MessageId'] . "\n";
    } catch (AwsException $e) {
        // If an error occurs, print the error message
        echo "Error: " . $e->getMessage() . "\n";
    }

The email does send and arrives in the mailbox properly. The console on the browser will show a 500 Error at jquery-3.6.4.js:10191. The code runs perfectly fine in a local environment, but when deployed to an AWS Linux 2 server it produces the 500 Error. Any ideas/suggestions on how to solve this issue?