Execute a pop-up window?

[listenmirndt]

Not using the onload or onclick but basically, I would like to trigger a popup in the following way:

<?php
if ($condition == 1) { popup here }
?>

Thanks!

[johanafm]

<?php
if ($condition == 1) { 	echo "<script type=text/javascript> window.open(); </script>"; }
?>

Just be aware that a pop-up on page load might be blocked by default by the browser (as firefox does).

[listenmirndt]

Thank you!!