Делай так:
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
</head>
<body>
<?
$name="Вася";
echo "dsfd";
?>
<script type="text/javascript">var nume="<? echo $name; ?>"</script>
<input type="button" id="but"name="but" value="nagzatj" onclick="alert (nume)"; >
</body>
</html>