php变量怎么赋值给js变量，php和js代码在同一个页面中

 php变量y赋值给js变量zifuchuan,<?php ?>外加单引号、双引号和不加引号，都不是变量y的内容，感觉是js无法识别php语句
这是部分代码
<?php
$y="120.5,30.2,120.2,30.4,120.5,30.5,118.9031,39.6994";
?>

<script> 
      var zifuchuan=<?php echo $y;?>;
      alert(zifuchuan);
</script>

 var zifuchuan='<?php echo $y;?>';//要用引号扩起来，要不就是 var zifuchuan=120.5,30.2,120.2,30.4,120.5,30.5,118.9031,39.6994;语法错误了