function getParamVal($param) {
	$val = (isset($_GET[$param]) && $_GET[$param] != '') ? $_GET[$param] : '';
	$val = htmlspecialchars($val, ENT_QUOTES);

	return $val;
}
$aaa = getParamVal('a');
echo 'AAA='.$aaa."
";

0001 function getParamVal($param) {
0002  $val = (isset($_GET[$param]) && $_GET[$param] != '') ? $_GET[$param] : '';
0003  $val = htmlspecialchars($val, ENT_QUOTES);
0004 
0005  return $val;
0006 }
0007 $aaa = getParamVal('a');
0008 echo 'AAA='.$aaa."
0009 ";

function getParamVal(param)
{
	var query = location.search;
	var regexp = new RegExp('[\\?&]' + param + '\=([^\&#]*)', 'i');
	var val = query.match(regexp) || '';
	return val[1] || '';
}
alert(getParamVal('a')); 

0001 function getParamVal(param)
0002 {
0003  var query = location.search;
0004  var regexp = new RegExp('[\\?&]' + param + '\=([^\&#]*)', 'i');
0005  var val = query.match(regexp) || '';
0006  return val[1] || '';
0007 }
0008 alert(getParamVal('a')); 
0009