Hello

so, instead of using header, try meta refresh like this

PHP Code:
echo '<meta http-equiv="refresh" content="0; URL=xy.php?job=done" />'; 
but it may be disabled, so try another way using javascript:

PHP Code:
echo '<script type="text/javascript">window.location="xy.php?job=done"</script>'; 
regards

Feras Jobeir