How to get value from popup window to parent window by clicking from database selection?

Originally it was like this and it worked until the crawlers no longer supported it, and even the return No. after the click I got there:

<scriptlanguage="JavaScript"type="text/javascript">var retVal=""var valReturned;function openModal(){
retVal=showModalDialog('stranky/modal.php');
valReturned=retVal;
document.getElementById("zakaznik").value=valReturned;}</script>...

How to get value from popup window to parent window by clicking from database selection?

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