<form id="upload" method="post" action="upload.php" enctype="multipart/form-data">
upload.php
<?php
// A list of permitted file extensions
$allowed = array('png', 'jpg', 'gif','zip');
if(isset($_FILES['upl']) && $_FILES['upl']['error'] == 0){
$extension = pathinfo($_FILES['upl']['name'], PATHINFO_EXTENSION);
if(!in_array(strtolower($extension), $allowed)){
echo '{"status":"error"}';
exit;
}
if(move_uploaded_file($_FILES['upl']['tmp_name'], 'uploads/'.$_FILES['upl']['name'])){
echo '{"status":"success"}';
exit;
}
}
echo '{"status":"error"}';
exit;в 21 строке echo '{"status":"error"}'; этот лишний наверно?