PHP undefined array key error in login function [duplicate]

ERROR : Undefined array key 'u_email'

and it says the same about 'u_pass'.

The names are correct. In database they're saved with the same name as well.

Here's my code:

function login(){
    if(isset($_POST['login'])){
        
        $email=$_POST['u_email'];
        $password=$_POST['u_pass'];
        include 'config/connections.php';
        if($email!="" && $password!=""){
        $q="SELECT* FROM users WHERE u_email= '$email' AND u_pass='$password'";
        
        $q_run=mysqli_query($con,$q);
        $data=mysqli_fetch_array($q_run);

        if($data['u_email']==$email && $data['u_pass']==$password){
            $_SESSION['id']=$data['u_id'];
            $_SESSION['name']=$data['u_name'];
            $_SESSION['email']=$data['u_email'];
            $_SESSION['password']=$data['u_pass'];

            ?>
            <div class="alert alert-success mt-3">Logging in. Please wait...</div>
            <script>
                            setTimeout(function(){
                                window.location='home.php';
                            }, 2000);
                        </script>
            <?php  
        }
        else{
            ?>
        <div class="alert alert-danger mt-3">Invalid Email or Password</div>
            <?php
        }
    }else{
            ?>
        <div class="alert alert-danger mt-3">Please Enter Email and Password</div>
            <?php
        }
    }
}

source https://stackoverflow.com/questions/70264643/php-undefined-array-key-error-in-login-function