Can't get json from php

Question

I am a beginner in php and wordpress. I try to make a simple plugin which can show 3 latest post and show them in the page. At first I want to get an array which has been already encoded in json, and then work with with js. But somewhere in the code I have a mistake or maybe I don't understand something important. There is my code which return nothing. If delete dataType in Ajax, will return whole code. Any advises will be appreciated. JS and PHP in one file.

   <button onclick='myAjax()'>Button</button>

<script type="text/javascript">
    function myAjax(){
        $.ajax({
            type: "GET",
            url: "plug_in.php",
            data: {action: "call_this"},
            dataType: 'json',
            success:function(data){
            alert(data);    
        }
        })
    };
</script>
<?
//Plugin name: My plagin 
//Description: This plugin for getting posts and posts they



function show_post(){

$args = array(
        'numberposts' => 3
    );
        $post = get_posts($args);
        $all_post = array();
        foreach ($post as $key) {
            array_push($all_post, $key->post_author,$key>post_title,$key>post_content,
            $key->post_date);
            }


            echo json_encode($all_post);
        };

        if($_GET['action'] == 'call_this'){
                show_post();
        };

?>

Answer 1

try this code

function show_post(){
    $args = array('numberposts' => 3);
    $post = get_posts($args);
    $all_post = array();
    foreach ($post as $key) {
        array_push($all_post, $key->post_author,$key-`enter code here`>post_title,$key>post_content,
        $key->post_date);
    }
    echo json_encode($all_post);
}

if($_GET['action'] == 'call_this'){
    show_post();
}