Using jQuery to fetch variable from my database - php

Question

I have done some reading and I think i need to use json for this. I have never used this before. I am trying to accomplish this, but in jQuery
$email_exist_check = mysqli_query($connect, "SELECT * FROM accounts WHERE email='$desired_email'") or die(mysql_error());
$email_exist = mysqli_num_rows($email_exist_check);
if ($email_exist == 0) {
//stop and make user write something else
} else {
//keep going
}
I am switching my website over from php to jQuery, which is also very new to me but seems so much better. Here is a piece of my jQuery. I am validating a form. The form works and submits, but now i want to see if the email exists in my database before submission. How would i do this?
if (email == "") {
$("#error5").css("display", "inline");
$("#email").focus();
return false;
}
// Im guessing the new code would go here
var dataString = $("#acc_form").serialize();
var action = $("#acc_form").attr('action');
$.ajax({
type: "POST",
url: action,
data: dataString,
success: window.location.assign("cashcheck_order.php")
});

Answer 1

This is a basic ajax call using jquery
var thing1; //thing 1 to use in js
var thing2; //thing 2 to use
var form = ("#acc_form"); //localize the form to a variable. you don't need to keep looking it up
var dataString = form.serialize();
var action = form.attr('action');
$.ajax({
url: action,
data: dataString,
type: "post",
success: function(data){
var responseData = $.parseJSON(data); //json native decoding if available, otherwise will do it with jquery
thing1 = responseData["thing1"];
thing2 = responseData["thing2"];
},
error: function(data){
console.log("error", data);
}
});
On the php side, to bring the vars in you use
$input1 = isset($_GET["name_of_input1"]) ? $_GET["name_of_input1"] : "";
if this is set, set this value, else set blank.
you can use $_POST, $_REQUEST if you prefer.
do not forget to sanitize your inputs.
Now to send it back to the js file
$dataToReturn = [
"thing1"=>"I'm thing 1",
"thing2"=>"I'm thing 2"
];
//sending back data
echo json_encode($dataToReturn);