只需要一个判断就好了
if(strpos($_SERVER['HTTP_USER_AGENT'], 'iPhone')||strpos($_SERVER['HTTP_USER_AGENT'], 'iPad')){
echo 'systerm is IOS';
}else if(strpos($_SERVER['HTTP_USER_AGENT'], 'Android')){
echo 'systerm is Android';
}else{
echo 'systerm is other';
}
?>