php - PHP function on submit button not working (with REQUEST_URI)

Question

I can't understand why this simple mailing php function I wrote doesn't work. It's installed inside a Wordpress page (that's why I used REQUEST_URI and not PHP_SELF). I'm just a php beginner, have I forgot something?

<?php
echo '<form method="post" action="';
echo $_SERVER['REQUEST_URI'];
echo '"><input type="image" name="blabla" src="/image-path/image.png"></form>';
    if ($_POST['blabla'])
    { 
        $to = 'email@emailadress.com';
    $subject = 'Test mail';
    $message = 'Test.';
    mail($to,$subject,$message);
    echo "Email sent.";
    }
?>

Answer 1

if(isset($_POST['blabla_x']) または isset($_POST['blabla'])) を試してください

画像を POST すると、ブラウザによっては、押した場所にポイントが送信されるためです。