猫叔，我这个按钮为什么获取不到，不起作用

<div class="col text-center">
	<input type="submit" name="button" id="button" value="修改" class="btn btn-outline- 
        secondary"> <input type="reset" class="btn btn-outline-danger">
</div>
<?php
if(isset($_POST['button']))
	{
		$username = $_POST['username'];
		$password = $_POST['password'];
		$phone = $_POST['phone'];
		$sql = "update user set username='$username',password='$password',phone='$phone' where id='$id'";
		$result=mysqli_query($link,$sql);
		if ($result)
		{
			echo "<script>alert('修改成功!');location.href='user_management.php';</script>";
		} 
		else
		{
			echo "<script>alert('修改失败!');location.href='user_management.php';</script>";
		}
	}
?>