php变量赋值给js

$(document).ready(function(){

<?php $f="'name'"?>
var t=<?php echo $f?>;
alert(t)

})

<script language="javascript" >
var t=<?php echo '"sd"'?>;
alert(t)
</script>

关键是sd两旁既要加单引号还要加上引号否则就会显示
“sd is not defined
[在此错误处中断]
var t=sd;”
sd不加引号即为一个变量，之前没定义过该变量，就把他赋值给别的变量，当然会报错