redirected you too many times. Try clearing your cookies. ERR_TOO_MANY_REDIRECTS
<?php
session_start();
$error = '';
?>
<!--login-->
<?php
if (isset($_SESSION['USER_ID'])) {
    header("Location:profile.php");
} elseif (!isset($_SESSION['USER_ID'])) {
    if (isset($_POST['login'])) {
        $json = $firebase->get(DEFAULT_PATH . "/ARCusers/");
        $json_ary = json_decode($json, true);
        $emailFound = FALSE;
        if (is_array($json_ary) || is_object($json_ary)) {
            foreach ($json_ary as $id => $val) {
                if ($_POST['email'] == $val['email'] && $_POST['password'] == $val['password']) {
                    if ($val['email verification'] == 1) {
                        $_SESSION['USER_ID'] = $id;
                        header("Location:email_form.php");
                    } else {
                        $error = 'Account dose not active, activate email';
                    }
                    $emailFound = TRUE;
                    break;
                }
            }
            if ($emailFound === FALSE) {
                $error = 'wrong email or password';
            }
        }
    }
}
?>