check whether the url isvalid or not

//function to check whether the url isvalid or not

function validUrl($url)
{
if(preg_match("/^((http:|https:)\/\/)[A_Za-z0-9_]*(\.)[a-zA-Z]*[?|&|[a-zA-Z0-9]]*/",$url))
return 1;
else
return 0;
}