jQuery获取输入框文本并使用$ post发送到php

Can anyone tell me how to do this? i use button to input data in the text input box. After that i want to click a b

As has been suggested use $.ajax()

The basic syntax is as follows:

$.ajax({
  url: '/path/to/file',
  type: 'default GET (Other values: POST)',
  dataType: 'default: Intelligent Guess (Other values: xml, json, script, or html)',
  data: {param1: 'value1'}
})
.done(function() {
  console.log("success");
})
.fail(function() {
  console.log("error");
})
.always(function() {
  console.log("complete");
});

In your case this can be simplified a little:

$("#add").click(function() {
  $.ajax({
    url: '/path/to/file',
    type: 'POST',
    data: {currentTotal: $display.val()},
    success: function(result){
      // here you will have access to the response from your PHP script
      // and can do something with it
    }
  });
});

In your PHP script, you'll then have access to the value posted, thus:

<?php
  $currTot = $POST['currentTotal'];

If you want your JavaScript to receive a return value, you'll have to echo it as the last thing in the PHP file:

<?php
  $currTot = $POST['currentTotal'];
  // do some processing to obtain $newTotal
  echo $newTotal