PHP函数补完：判断变量是否为数字is_numeric()

$tests = array(
    "42", 
    1337, 
    "1e4", 
    "not numeric", 
    array(), 
    9.1
);
foreach ($tests as $element) {
if (is_numeric($element)) {
echo "'{$element}' is numeric", PHP_EOL;
} else {
echo "'{$element}' is NOT numeric", PHP_EOL;
}
}

'42' is numeric
'1337' is numeric
'1e4' is numeric
'not numeric' is NOT numeric
'Array' is NOT numeric
'9.1' is numeric

	$id = 0xff33669f;
	if (is_numeric($id)) 
	echo $id, '符合要求。';//output 4281558687符合要求。
	else 
	echo $id, '不符合要求。';