使用Javascript设置隐藏字段值； 使用PHP post方法发送数据

Question

I need to get the user's screen resolution and save it my database.

What I'm doing is this: I have a Javascript function called with that gets the info and passes the value to a hidden form field. This is the function:

<script type="text/javascript">

function getUserData(){

var s_width=screen.width
var s_height=screen.height
document.getElementById('screen_width').value=s_width
document.getElementById('screen_height').value=s_height

}

</script>

And the form:

<form name="login" id="login" action="memberlogin.php" method="post">
<input type="hidden" id="screen_width" name="screen_width">
<input type="hidden" id="screen_height" name="screen_height">
<table style="margin-top:9px;">
<tr><td width="200px"><input type="text" name="username" style="width:100%"/></td></tr>
<tr><td width="200px"><input type="password" name="password" style="width:100%"/></td></tr>
<tr><td><input type="submit" name="submit" value="Log In" /></td></tr>
</table>
</form>

The form submits to the same page. When I click 'submit' and try to echo the value of $_POST['screen_width'] and $_POST['screen_height'], nothing happens. But when I re-submit it, the values are there. Can someone tell me what am I doing wrong? If you have an alternative solution, it would be equally appreciated.

Answer 1

have you checked firebug's output? maybe there are some errors? try alert sth in your function, maybe it isn't called after initial page load? try putting function call in submit button's onClick or form's onSubmit event.

Answer 2

我自己解决了它，这只是在加载元素之后调用函数的问题。