jQuery AJAX .post从一个php中提取多个变量

I am trying to find the best way to pull multiple variables from PHP with an AJAX post. Right now, I am using .substr to split an echoed variable from the PHP itself.

Here's my AJAX post (with jQuery)

$.post("scripts/enter/register.php", {username : username, email : email, password : password}, function(data) {
    var callback = data.substr(0,1);
    var user_session = data.substr(1);
    if(callback === "1"){
        //Do a registration script
    } else {
        //Give an error
    }
});

and my PHP

if (strlen($hash) >= 20) {
    if($user_name){
        //Perform SQL queries
        echo "1";
        echo $cookie;
    } else {
        echo "0";
    }
} else {
    echo "0";
}

As you see, in my php, I echo two variables when everything goes well. When there's an error, I only echo one variable. This script works perfectly fine, but I find it clunky and apparently it is unsecure. On a side note, I have come to understand echo is not secure, though no one has told me what to instead.

I have another script that handles login (this last script is register), but I use a different PHP script. Here are the questions:

1. Can I combine both register and login (and any other PHP scripts) into a single script?
2. Is there a better way to turn the PHP variables into javascript variables to be able to use in the jQuery?

you have if(callback === "1"){ in your code.

This should be if(callback == "1"){ assuming this may be a number as well as a string

That may solve part of your problem