login.php

<script src="https://accounts.google.com/gsi/client" async defer></script>
<div id="g_id_onload"
     data-client_id="34178471422-5chptlf4ujd05p5a6suhvglmcc2f9jgk.apps.googleusercontent.com"
     data-callback="onSignIn"
     data-auto_prompt="false"
     data-ux_mode="redirect"
     data-login_uri="http://localhost/public_html/index.php">
</div>
<div class="g_id_signin" data-type="standard"></div>

<script>
    function onSignIn(response) {
        const { id_token, access_token, email } = response.credential; // Include email in response

        fetch('google_signin.php', {
            method: 'POST',
            headers: {
                'Content-Type': 'application/json',
            },
            body: JSON.stringify({ id_token, access_token, email }), // Include email in JSON
        })
        .then(response => response.json())
        .then(data => {
            if (data.success) {
                // User's email address is valid, create a session and log them in
                // Implement your session creation and login logic here
                console.log('User is authenticated and can be logged in.');
                // You can redirect to index.php here
                // window.location.href = 'index.php';
            } else {
                // Display an error message or prompt the user to create a new account
                console.error('User email address not found in the database:', email);
            }
        })
        .catch(error => {
            console.error('Server verification failed:', error);
        });
    }
</script>