how to read and write database data for logged in user

Question

I have no idea how anyone who actually read this would equate it with "How do you run WordPress functions in PHP?". I have zero interest in running WordPress functions in PHP. My question is about identifying the user / session who submitted the HTTP request.

It does happen to be true that when you load a page, you can use the WordPress get_current_user_id() function to identify the user. But that doesn't make the question about running WordPress functions.

I'm building a site with WordPress, Javascript, and PHP. I have PHP scripts that recognize the WordPress user id, get_current_user_id(), of the user who is logged in when the page loads. However, when I try to send an HTTP request to execute a PHP script via Javascript XMLHttpRequest, the PHP file doesn't recognize the user id from get_current_user_id().

I thought using PHP sessions would help, but they don't.

So, how do I enable the user to write data?

`get_current_user_id()` is a WP function. If you haven't included WP in your PHP file server dies with `PHP Fatal error: Uncaught Error: Call to undefined function get_current_user_id() i` error. See: https://stackoverflow.com/questions/15304926/how-to-include-wordpress-functions-in-custom-php-file. — mx0, Aug 20 '18 at 15:48
Possible duplicate of [How to include Wordpress functions in custom .php file?](https://stackoverflow.com/questions/15304926/how-to-include-wordpress-functions-in-custom-php-file) — mx0, Aug 20 '18 at 15:50

score 1 · Answer 1 · answered Aug 26 '18 at 02:02

I discovered that the PHP session ID is stored in a cookie. It appears in the cookie string as "...;PHPSESSID=fkldsjflksjlf;...". In my Javascript XMLHttpRequest script, I use the following to extract the session ID from the cookie. Then I send it as a parameter.

function test() {
    var idBegin = document.cookie.indexOf("PHPSESSID=") + 10;
    var sessId = document.cookie.substring(idBegin)
    var idEnd = sessId.indexOf(";");
    sessId = sessId.substring(0, idEnd);

    var request = new XMLHttpRequest();
    request.open("GET", "test.php?sessid="+sessId, true);
    request.onreadystatechange = function () {
        if (request.readyState === 4) {
            if ((request.status === 200) || (request.status === 0)) {
            }
        }
    };
    request.send(null);
}

On the server side, I have a table "UserSessions" in my MySQL database. The table has two columns: SessionID; and UserID. I have a PHP script that executes when the user loads a page. At this point, the get_current_user_id() function is available to get the WordPress user ID and $_COOKIE["PHPSESSID"] is available. The PHPSESSID is what's stored as a cookie on the client.

<?php

$sql = "INSERT INTO UserSessions (SessionID, UserID)";
$sql = $sql . " VALUES (" . $_COOKIE["PHPSESSID"] . ",";
$sql = $sql . get_current_user_id() . ")";

// I user the standard MySQLi stuff to execute the query and
// store the session ID, user ID pair

?>

In PHP the scripts I execute via Javascript, I include the following

<?php

$sql = "SELECT UserID FROM UserSessions ";
$sql = $sql . " WHERE SessionID = " . $_GET["sessid"];

// Again, standard MySQLi stuff to execute the query
// and retrieve the user id based on the session ID.
// I store the retrieved value in variable "$userid"

// When I have the user id, I can use it in other tables
// that have a UserID column

$sql = "SELECT column FROM table ";
$sql = $sql . " WHERE UserID = " . $userid;

$sql = "INSERT INTO table (column) VALUES (data) ";
$sql = $sql . " WHERE UserID = " . $userid;

?>

This doesn't seem like the right way to do it. It works for me. And I don't know how to do it better. By all means, tell me it's incorrect and give me the correct way to do this. Thanks.

how to read and write database data for logged in user

1 Answers1