PHP Script running without redirection - php

Question

I have a database with two tables: accounts and recipes(each have their own ID column).
I have a page that displays all the recipes. I want to enable users to add recipes to their favourites in accounts table. Once user is logged in, $_SESSION['user_id'] is set.
I have script that will add the recipe id to the favourites in accounts table, but I don't know how to run it without redirecting from the page that displays all recipes.
Here is what i have so far:
_view.php
<?php
$result = $mysqli->query("SELECT * FROM recipes");
if ( $result->num_rows == 0 ){
$_SESSION['message'] = "Error!";
echo "<div class='error-mess'>" . $_SESSION['message'] . "</div>";
}
else {
while ($row = mysqli_fetch_array($result)) {
$slug = $row['slug'];
$ingr = json_decode($row['ingr']);
$ingr_count= count($ingr);
$id = $row['id'];
echo '<div class="container recipe mb-2">';
echo '<img class="" src="/images/recipes/';
echo $row['img'];
echo '"/>';
echo '<div class="title-cats"><a href = "/recipe_preview.php?slug=' . $slug . '">';
echo $row['title'];
echo '</a></div>';
echo '<h4>Ingredients:</h4><br>';
for($i = 0; $i<$ingr_count;$i++){
$num = $i + 1;
echo $num . '. ';
$ingrs = json_decode($ingr[$i],true);
print_r($ingrs[0]);
echo '<br>';
}
echo '<br><button type="submit" class="btn" name="add">Read More</button>';
//favourites link
echo '<span class="fa fa-heart ml-3"></span>';
echo '</div><hr>';
}
}
_favourite.php
<?php
//relationship
require 'db.php';
$user_id = $_SESSION['user_id'];
//$favourite_id = $_POST['fav'];
$favourite_id = $_GET["id"];
echo $favourite_id;
echo $user_id;
$result = $mysqli->query("SELECT favourites FROM accounts WHERE id ='$user_id'");
if ( $result === null) {//doesnt work
$favs = array();
array_push($favs,$favourite_id);
$new_favs = json_encode($favs);
echo 'null';
}
else{
$favs = array();
$result = json_decode($result,true);
array_push($favs, $result);
array_push($favs,$favourite_id);
$new_favs = json_encode($favs);
}
$sql = "UPDATE accounts SET favourites ='$new_favs' WHERE id = '$user_id'";
if ( $mysqli->query($sql)){
echo '<div class="error-mess">Recipe sucessfully saved!</div>';
}
else{
echo '<div class="error-mess">NOT</div>';
}
.js -jquery library is there
$(document).ready(function() {
$('#favourite').click(function(e) {
e.preventDefault(); // prevents the default behaviour of following the link
$.ajax({
type: 'GET',
url: $(this).attr('href'),
data: {
id: $(this).data('id'),
},
dataType: 'text',
success: function(data) {
// do whatever here
if(data === 'success') {
alert('Updated succeeded');
} else {
alert(data); // perhaps an error message?
}
}
});
});
});