Sanırım aşağıda ki gibi olacak;

<script type="text/javascript">
var Tawk_API=Tawk_API||{};
var Tawk_LoadStart=new Date();
<!-- rest of the tawk.to widget code -->

<script type="text/javascript">
Tawk_API.onLoad = function(){
Tawk_API.setAttributes({
'name' : '<?php echo $uye_bilgileri['ad'].' '.$uye_bilgileri['soyad'];?>',
'email': '<?php echo $uye_bilgileri['email'];?>',
'phone' : '<?php echo $uye_bilgileri['telefon'];?>',
'hash' : '<?php echo hash_hmac("sha256","<?php echo $uye_bilgileri['email'];?>","buraya paneldeki api gelecek sanırım"); ?>'
}, function (error) {});

};
</script>
<!--End of Tawk.to Script-->