为什么要使用admin-ajax.php，它如何工作？

1)为什么使用admin-ajax.php而不是在单独的json中编码 像themes/example/json.php这样的文件,并在那里编码您的数据?

使用admin-ajax.php意味着WordPress核心已加载并可用.否则,您将需要手动加载所需的文件,这是一个复杂的过程,如果您不太了解Core,则很容易失败.而且,您对Javascript安全性有多好?

2)admin-ajax.php如何工作?我对此并不了解 文件.它会加载所有功能,以便您准备使用它们吗?

1. 它会加载WordPress核心,这意味着您可以使用$wpdb之类的东西 和$WP_Query.那是通过第25行.
2. 它发送一些头文件-行37-41.
   
   1. 内容类型标题
   2. 标头,告诉浏览器不要缓存结果
   3. 有趣的标头是由 send_nosniff_headers()
   发送的标头
   4. 和 nocache_headers() .
3. admin_init钩子触发.
4. 核心动作是动态定义和注册的-第46-73行. 除非需要,否则不会注册这些文件-即除非 通过$_GET或$_POST请求它们.
5. 触发"心跳" API钩子-第75行
6. 已检查请求用户的"已登录"状态,并且 触发了适当的管理或"无特权"挂钩.

项目#1和#6是使用AJAX API的主要原因.您拥有几乎肯定需要的WordPress Core,并且具有与其余WordPress相同的登录安全系统.

1) Why use admin-ajax.php instead of encoding your json in a separate file like themes/example/json.php and encode your data there?

Using admin-ajax.php means that the WordPress Core is loaded and available. WIthout that, you would need to hand load the files you need, which is a complicated process and prone to failure if you don't know the Core very, very well. And, how good are you with Javascript security?

2) How does admin-ajax.php work? I don't understand much from that file. Does it load all the functions so you are ready to use them?

1. It loads the WordPress Core, meaning you can use things like $wpdb and $WP_Query. That is through about line 25.
2. It sends a few headers-- lines 37 - 41.
   
   1. A content type header
   2. A header to tell browsers not to cache the results
   3. The interesting headers are those sent by send_nosniff_headers()
   4. and nocache_headers().
3. The admin_init hook fires.
4. Core actions are defined and registered dynamically-- lines 46 - 73. These won't be registered unless they are needed-- that is, unless they are requested via $_GET or $_POST.
5. The "heartbeat" API hook fires-- line 75
6. The "logged in" status of the requesting user is checked and the appropriate administrative or "no priviledge" hook is fired.

Items #1 and #6 are the primary reasons to use the AJAX API, in my opinion. You have the WordPress Core, which you almost certainly need, and you have the same login security system as with the rest of WordPress.

admin-ajax.php是WordPress AJAX API 的一部分,是的,它确实可以处理来自后端和前端的请求. 在这里,我想出了您的问题:

2)admin-ajax.php如何工作?

对于逻辑,您可以访问这里.

这假定您已经知道如何使JavaScript入队等.

JavaScript片段:

 jQuery(document).ready(function($) {

    // We'll pass this variable to the PHP function example_ajax_request
    var fruit = 'Banana';

    // This does the ajax request
    $.ajax({
        url: ajaxurl,
        data: {
            'action':'example_ajax_request',
            'fruit' : fruit
        },
        success:function(data) {
            // This outputs the result of the ajax request
            console.log(data);
        },
        error: function(errorThrown){
            console.log(errorThrown);
        }
    });   

});
 

PHP片段:

 function example_ajax_request() {

    // The $_REQUEST contains all the data sent via ajax 
    if ( isset($_REQUEST) ) {

        $fruit = $_REQUEST['fruit'];

        // Let's take the data that was sent and do something with it
        if ( $fruit == 'Banana' ) {
            $fruit = 'Apple';
        }

        // Now we'll return it to the javascript function
        // Anything outputted will be returned in the response
        echo $fruit;

        // If you're debugging, it might be useful to see what was sent in the $_REQUEST
        // print_r($_REQUEST);

    }

    // Always die in functions echoing ajax content
   die();
}

add_action( 'wp_ajax_example_ajax_request', 'example_ajax_request' );

// If you wanted to also use the function for non-logged in users (in a theme for example)
 add_action( 'wp_ajax_nopriv_example_ajax_request', 'example_ajax_request' );
 

1)为什么使用admin-ajax.php而不是用单独的json编码 像themes/example/json.php这样的文件,并在那里编码您的数据?

可能有帮助. admin- ajax.php与用于Ajax请求的自定义页面模板

admin-ajax.php is part of the WordPress AJAX API, and yes, it does handle requests from both backend and front. here what i figure-out for your question that is:

2) How does admin-ajax.php work?

for the logic you can visit here.

This assumes you already know how to enqueue JavaScript, etc.

JavaScript Piece:

jQuery(document).ready(function($) {

    // We'll pass this variable to the PHP function example_ajax_request
    var fruit = 'Banana';

    // This does the ajax request
    $.ajax({
        url: ajaxurl,
        data: {
            'action':'example_ajax_request',
            'fruit' : fruit
        },
        success:function(data) {
            // This outputs the result of the ajax request
            console.log(data);
        },
        error: function(errorThrown){
            console.log(errorThrown);
        }
    });   

});

PHP Piece:

function example_ajax_request() {

    // The $_REQUEST contains all the data sent via ajax 
    if ( isset($_REQUEST) ) {

        $fruit = $_REQUEST['fruit'];

        // Let's take the data that was sent and do something with it
        if ( $fruit == 'Banana' ) {
            $fruit = 'Apple';
        }

        // Now we'll return it to the javascript function
        // Anything outputted will be returned in the response
        echo $fruit;

        // If you're debugging, it might be useful to see what was sent in the $_REQUEST
        // print_r($_REQUEST);

    }

    // Always die in functions echoing ajax content
   die();
}

add_action( 'wp_ajax_example_ajax_request', 'example_ajax_request' );

// If you wanted to also use the function for non-logged in users (in a theme for example)
 add_action( 'wp_ajax_nopriv_example_ajax_request', 'example_ajax_request' );

1) Why use admin-ajax.php instead of encoding your json in a separate file like themes/example/json.php and encode your data there?

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