PHP变量的非空判断

[tjzero_sapce]

在php中，我以sso.php为基础新建的erp_sso.php中有

$erpvalidate = $_GET['erpvalidate'];

这个erpvalidate 是特殊情况下我才会把它挂在url后面的一个参数,也就是说某些情况下erpvalidate 种是不带有任何值的,那么我在erp_sso.php中已经有一个js判断了

<script language="javascript" type="text/javascript">
    window.onload = function(){
		var forumdisplayhtm_hide = document.getElementById('forumdisplayhtm_hide');
		var headerhtm_hide = document.getElementById('headerhtm_hide');
		var footer_hide = document.getElementById('footer_hide');
		if("$erpvalidate" != null && "$erpvalidate" != ""){
			alert(123);
			forumdisplayhtm_hide.style.display = "none";
			headerhtm_hide.style.display = "none";
			footer_hide.style.display = "none";
		}
	}
</script>

但是在我的url后面不带有erpvalidate参数的情况下,这里的js判断每次都能会弹出alert, 请问php中,在erpvalidate参数不存在的情况下,怎么判断这个$erpvalidate 呢?

[xuzuning]

if(is_set($_GET['erpvalidate']))
$erpvalidate = $_GET['erpvalidate'];

[PIGer920]

if(strlen($xxx)==0){
echo "kong";
}

[tjzero_sapce]

[Quote=引用 1 楼 xuzuning 的回复:]
if(is_set($_GET['erpvalidate']))
$erpvalidate = $_GET['erpvalidate'];
[/Quote]
您写的这个是用在php中的吧? 我需要的是能用在js中的

[tjzero_sapce]

[Quote=引用 2 楼 piger920 的回复:]
if(strlen($xxx)==0){
echo "kong";
}
[/Quote]

<script language="javascript" type="text/javascript">
    window.onload = function(){
		var forumdisplayhtm_hide = document.getElementById('forumdisplayhtm_hide');
		var headerhtm_hide = document.getElementById('headerhtm_hide');
		var footer_hide = document.getElementById('footer_hide');
		if(strlen($erpvalidate)==0){
			alert(123);
			forumdisplayhtm_hide.style.display = "none";
			headerhtm_hide.style.display = "none";
			footer_hide.style.display = "none";
		}else{
			alert(321);
		}
	}
</script>

不行,他说我这个 $erpvalidate is undefined

[xuzuning]

if("$erpvalidate" != null && "$erpvalidate" != ""){

中，$erpvalidate是什么？php变量？
没有看到有读取url参数的代码

[foolbirdflyfirst]

<?php $erpvalidate = $_GET['erpvalidate'];?>

<script language="javascript" type="text/javascript">
    window.onload = function(){
        var forumdisplayhtm_hide = document.getElementById('forumdisplayhtm_hide');
        var headerhtm_hide = document.getElementById('headerhtm_hide');
        var footer_hide = document.getElementById('footer_hide');
        var ed = '<?php echo $erpvalidate;?>';
        if(ed != 'null' && ed != ""){
            alert(123);
            forumdisplayhtm_hide.style.display = "none";
            headerhtm_hide.style.display = "none";
            footer_hide.style.display = "none";
        }
    }
</script>

[foolbirdflyfirst]

js代码是客户端的东西,php是服务器端的东西.这个得分清楚.

[tjzero_sapce]

[Quote=引用 6 楼 foolbirdflyfirst 的回复:]
PHP code
<?php $erpvalidate = $_GET['erpvalidate'];?>

<script language="javascript" type="text/javascript">
window.onload = function(){
var forumdisplayhtm_hide = document.getElement……
[/Quote]
这个方法很好使 不过我的那个 $erpvalidate 在前面是被赋值 hide 的,那么在

if(ed == 'hide' ){
            alert(123);
            forumdisplayhtm_hide.style.display = "none";
            headerhtm_hide.style.display = "none";
            footer_hide.style.display = "none";
        }

也是可以的