如何在MySQL查询中使用JavaScript变量

Question

我想在mysql查询中获取javascript变量。我使用了此代码，但未在查询中获取值。

echo "<script>

$('#customer_name').change(function(){
var cusno=$('#customer_id').val();

alert(cusno);";

$query="select id from invoice WHERE cus_id =('"+cusno+"') and `sale_type` 
!= 1";

 $cmd = mysqli_query($GLOBALS['conn'] ,$query);
 $rowcount=mysqli_num_rows($cmd);

 if($rowcount>0){
 echo"
 var AP=document.getElementById('test');
 AP.innerHTML='Allocated Payment';
 ";
 }
 else{}

 echo"
 })";
  </script>