php - メールを送信する関数を作成しようとしていますが、うまくいきません..php を初めて使用しています...何が間違っていますか?

Question

function SendEmail() {

    $to      = $email;  
    $subject = 'Sales | Purchase Instructions';  
    $message = ' 

    Thank you for your purchasing 'My Product'.

    Your account information 
    ------------------------- 
    Name:   'Your Name'
    Email:  'Your Email' 

    ------------------------- 

    You can purchase our product by clicking on the purchase button, entering product name, and quantity in the provided boxes, and then click purchase.;  
    $headers = 'From:My Company <me@mycompany.net>' . "\r\n";  


mail($to, $subject, $message, $headers);  
}