Never use javascript:
URLs. Put the URL in the href
attribute where it belongs:
$a= '<a href="a2.php" onclick="LaunchPopup(this.href, 250, 1); return false;">ciciş yap</a>';
Now not only do you not have to worry about the escaping (assuming you can get away with passing numbers as the other arguments), but also your link now works properly when middle-clicked or bookmarked, instead of giving a JavaScript error.
Better still, unobtrusive scripting:
<a href="a2.php" class="popup">ciciş yap</a>
<script type="text/javascript">
for (var i= document.links.length; i-->0;) {
if (document.links[i].className==='popup') {
document.links[i].onclick= function() {
LaunchPopup(this.href, '250', '1');
return false;
}
}
}
</a>
Keep script code in scripts and out of markup, then you don't have to worry about HTML-escaping.