AJAX函数在PHP文件中访问PHP函数

I have a working AJAX file that will execute the content in a PHP file. However, if the php is within the function(there are alot of php funtion in a PHP file), how do I call only the function that I want.

My AJAX code:

$(document).ready(function(){

// use ajax, call the PHP
$.ajax({
    url: 'postme.php', 
    success: function(response){
        $('.result_Postme').text(response);
    }
})
});

one of the function in postme.php PHP file:

<?php 
  function echo()
  {
    echo 'Text';
  }
?>

Thanks.

EDIT:

@Amadan hi, i tried ur method but it doesn't seems to be outputting in the html.

My AjAx code:

$(document).ready(function(){

// use ajax, call the PHP
$.ajax({
    url: 'rank.php', 
    data: {
        action: 'echo'
    },
    success: function(response){
        $('.rank_Alibaba').text(response);
    }
})
});

PHP file

switch($_REQUEST['action']) 
{
 case 'echo': 
 echo "text";
 break;
 }

HTML:

 <td class="rank_Alibaba"></td>

a) Use a MVC framework, such as Laravel or CakePHP. Such frameworks are quite opinionated and will force best practices on you, whether you want them or not. :P

b) If you absolutely want to stick with plain PHP, the easiest way is to pass a parameter to select your function, and then in your PHP file have a switch statement on that parameter that will dispatch the call to the correct place. For example, in JavaScript:

...
url: 'postme.php', 
data: {
  action: 'echo'
},
...

In PHP:

switch($_REQUEST['action']) {
  case 'echo':
    echo();
    break;
  ...
}

You need to call the function in your PHP file:

Append a line in the end.

   <?php 
    function yourFunc() {
      echo 'Text';
    }
    yourFunc()
    ?>

How come PHP parser know that you need to execute the code from the function.

You cannot directly call a php function through javascript. What you can do is something like a "dispatcher".

$(document).ready(function(){

    // use ajax, call the PHP
    $.ajax({
        url: 'postme.php', 
        data: { func: "echo" }
        success: function(response){
            $('.result_Postme').text(response);
        }
    })
});

and in php:

<?php 
  if($_REQUEST["func"] == "echo") {
    echo();
  } elseif(....) {

  }

  function echo()
  {
    echo 'Text';
  }
?>

You have to control the php behaviour according to the input query.

Add this to your php script and may be work(just a sample):

<?php 
  if(isset($_GET['action']) && $_GET['action']) == 'echo'){
    echo();
  }else{
    // original behaviour
  }
  function echo()
  {
    echo 'Text';
  }
  // whatever function else
?>

And change your javascript to:

$(document).ready(function(){

// use ajax, call the PHP
$.ajax({
    url: 'postme.php?action=echo', 
    success: function(response){
        $('.result_Postme').text(response);
    }
})
});

You can even make use of the $_GET var like this.

$.ajax({
    url: './inc/postme.php?argument=myFunction',
    type: 'POST',
    data: selected
    success: function(response){
        $('.result_Postme').text(response);
    }
});

and on the php side:

if($_GET['argument'] == 'myFunction'){
    //code here
}

I have 3 files: 1-Javascript 2-ADMIN.php 3-Class.php (where I store my functions)

In java script I use AJAX and JSON and allways send a objectEvent (ObjEvn) to ADMIN.php:

    //Your javaScript code
    $(document).on("event", "#idElement", function(){
        //Data you want to send to php evaluate
         var dt={ 
                  ObjEvn:"btn_Login",//This is the controller to ADMIN.php
                  dataJsToPHP: $("#txt_EmailLogin").val(),
                  asManyasYouWant: use jQuery to grab values....
                };

        //Ajax      
         var request =$.ajax({//http://api.jquery.com/jQuery.ajax/
                                url: "ADMIN.php",
                                type: "POST",
                                data: dt,
                                dataType: "json"  
                            });

        //Ajax Done catch JSON from PHP 
            request.done(function(dataset){
                for (var index in dataset){ 
                     dataPHPtoJsJS=dataset[index].dataPHPtoJs;
                     asManyasYouWantJS=dataset[index].asYouWant;
                 }

                 //JavaScript conditions. Here you can control the behaivior of your //html object, based on your PHP response
                 if(dataPHPtoJsJS){
                    $( "#idYourHtmlElement" ).removeClass( "class1" )
                    $( "#idYourHtmlElement" ).addClass( "class2" )
                 }


         }); 

        //Ajax Fail 
            request.fail(function(jqXHR, textStatus) {
                alert("Request failed: " + textStatus);
            }); 
    }

Now in ADMIN.php

$ObjEvn=$_POST["ObjEvn"];//Call this before all test
$asManyasYouWant = $_POST["asManyasYouWant "];

if($ObjEvn==="btn_Login"){
$login=$_POST["login"];
$passwd=$_POST["passwd"];
//call your function to test login in class.php
//finally, at the end, return your result to jquery. It could be another jquery code to //be loaded dynamiclly, it could be a html tag, it could be a value... it could be almost //everyting..
$arrToJSON = array(
        "dataPHPtoJs"=>"yourData",
        "asYouWant"=>"<div class=\".class1\">soemting</div>"    
        );  
        return json_encode(array($arrToJSON));
}
elseif($ObjEvn==="btn_NewUser"){
//retrieve anoter values
//and call your functions to create new user
//finally, at the end, return your result to jquery. It could be another jquery code to //be loaded dynamiclly, it could be a html tag, it could be a value... it could be almost //everyting..
$arrToJSON = array(
        "dataPHPtoJs"=>"yourData",
        "asYouWant"=>"<div class=\".class1\">soemting</div>"    
        );  
        return json_encode(array($arrToJSON));
}