从ajax发送数据到php

  <script>
      var er ="hi";

      $( "#save" ).click(function() {
      var er = $('#edit').val();
      alert(er);

    });

 $.ajax({  
    type: 'POST',  
    url: 's.php', 
    data: { er:er},
    success: function(response) {
        alert(er);
                                }
            });
  </script>

You must write the ajax code in click function, otherwise ajax code will execute on page load.

var er ="hi";

$( "#save" ).click(function() {
   var er = $('#edit').val();
   alert(er);
   $.ajax({  
     type: 'POST',  
     url: 's.php', 
     data: {'er':er},
     success: function(response) {
        alert(er);
     }
   });
});

Try above code. it will work for you.