引导登录按钮不会重定向到登录页面

由于某些原因，按钮不起作用，它只是刷新页面。有人能提供一些信息吗？我是新手。

"登录"按钮应向$_POST['submit'])发送操作并继续执行登录功能。表单数据必须发送到同一页。

<?php
if(isLoggedIn()) { redirect(); }
// Login Process
if(check_value($_POST['submit'])) {
    $userLogin = new login();
    $userLogin->validateLogin($_POST['employee_number'], $_POST['password']);
}
?>  
<div class="col-md-4 col-md-offset-4">
    <div class="panel panel-default">
        <div class="panel-heading">
            <h3 class="panel-title">
                <small>Sign in</small>
            </h3>
        </div>
        <div class="panel-body">
            <form action="" method="post">
                <div class="row">
                    <div class="col-xs-7 col-sm-7 col-md-7">
                        <div class="form-group">
                            <input type="text" name="employee_number" class="form-control input-sm" placeholder="Employee number">
                        </div>
                    </div>
                </div>
                <div class="row">
                    <div class="col-xs-7 col-sm-7 col-md-7">
                        <div class="form-group">
                            <input type="password" name="password" class="form-control input-sm" placeholder="Password">
                        </div>
                    </div>
                </div>
                <div class="form-group last">
                    <div class="col-sm-offset-3 col-sm-9">
                        <button type="submit" class="btn btn-success btn-sm" id="submit">Sign in</button>
                        <button type="reset" class="btn btn-default btn-sm">Reset</button>
                    </div>
                </div>
            </form>
        </div>
    </div>
</div>

/**
 * check_value
 * Looks for valid value and setted ones.
 */
function check_value($value) {
    if((@count($value)>0 and !@empty($value) and @isset($value)) || $value=='0') {
        return true;
    }
}