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问题:
I've been trying to figure this out for hours, though I'm too uneducated in web development to understand. Heres the case:
Another website has a script that they obtain information from the following way:
var url = "numbers.php"; parameters = "scoreid=" + document.getElementById('whatscore').value; parameters += "&num=" + document.getElementById('num1b1').value; xmlhttp2=GetXmlHttpObject(); if (xmlhttp2==null) { alert ("Your browser does not support XMLHTTP!"); return; } xmlhttp2.onreadystatechange = function() { if (xmlhttp2.readyState==4) { scorespot.innerHTML=xmlhttp2.responseText; // load setScores(document.getElementById('gradelvl').value); // set document.getElementById('submitscorebtn').style.display="none"; } } xmlhttp2.open("POST",url,true); xmlhttp2.setRequestHeader("Content-type", "application/x-www-form-urlencoded"); xmlhttp2.setRequestHeader("Content-length", parameters.length); xmlhttp2.setRequestHeader("Connection", "close"); xmlhttp2.send(parameters);
I've attempted to do the same thing, though when I attempt it I get the cross-origin error. I know their are ways to do it with jsonp and other things, though I have no clue where to start at all for this.
When I attempt to directly request information from their page, the numbers.php page, such as example.com/numbers.php?scoreid=131&num=41 . I always get returned with "Error: incorrect parameter syntax".
Can anybody please tell me how I would fix this in my case? I only know PHP and Javascript well, I'm very uneducated with Ajax and other things or external libraries.
I appreciate all help whatsoever! NOTICE: I DO NOT HAVE ACCESS TO THE WEBSERVER.
回答1:
If you do not have access to your server configuration, and if you do not control the external php script (assuming it's not set up to serve as a reverse proxy), then you absolutely cannot use a standalone javascript solution for this.
Rather, you would have to make the external request from your own local php script. Then you would call your local php script from Ajax, and this will work since you are accessing a local file, and thus not violating CORS.
Here is an example of an Ajax call thru a local PHP script.
Imagine a scenario where you allow users to lookup an album name. The user enters the name of the song, and the artist. You make a request to a 3rd party api, and return the response back to the user via a JavaScript alert notification. For this example, assume the user enters 'Black' and 'Pearl Jam' as the song and artist names
Ajax POST to Local PHP Script with HTML Example:
<html> <head> <!-- Load jQuery Library from Google --> <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"> </script> </head> <body> <h1> Ajax to local PHP Script Example: </h1> <form id="getArtist"> Artist: <input type="text" placeholder="Pearl Jam"> Song: <input type="text" placeholder="Black"> <input type="submit" value="Click Here to Active Ajax Call"> </form> </body> </html> <script type='text/javascript'> $("#getArtist").submit(function(event) { //Listen to when the Submit is pressed event.preventDefault(); //Stop the submit from actually performing a submit $.post("local_script.php", { song: "Black", artist: "Pearl Jam", dataType: "json"}) //prepare and execute post .done(function(response) { //Once we receive response from PHP script //Do something with the response: alert("The album name is: " +response); //Look into JSON.parse and JSON.stringify for accessing data }); }); </script>
PHP GET
<?php $url = 'http://api.music.com/album'; $song = urlencode($_GET['song'])); //Need to url encode $artist = urlencode($_GET['artist']); //Need to url encode $response = file_get_contents($url .'?song=' .$song .'&artist=' .$artist); //**The url looks like http://api.music.com/album?song=Black&artist=Pearl+Jam //** For purposes of this demo, we will manually assume the JSON response from the API: $response = '{ "album": "Ten" }'; //(Raw JSON returned by API) echo $response; //Return the response back to AJAX, assuming it is already returned as JSON. Else encode it json_encode($response)
PHP POST (using curl)
<?php $url = 'http://api.music.com/album'; $song = urlencode($_GET['song'])); //Need to url encode $artist = urlencode($_GET['artist']); //Need to url encode //$headers = array("Key: " ."Value","Key: " ."Value", //Set any headers, if required. $post = 'song=' .$song .'&artist=' .$artist; //Prepare Post parameters /* Configure Curl */ $ch = curl_init(); curl_setopt($ch, CURLOPT_URL, $url); curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); //Allow music api to send response curl_setopt($ch, CURLOPT_POST, 1); //Signifyd that we are doing a POST request curl_setopt($ch, CURLOPT_POSTFIELDS, $post); //curl_setopt($curl, CURLOPT_HTTPHEADER, $header); //Only if you need to send headers /* Get Response */ $response = curl_exec($ch); //** For purposes of this demo, we will manually assume the JSON response from the API: $response = '{ "album": "Ten" }'; //(Raw JSON returned by API) echo $response; //Send response back to Ajax, assuming it was already returned in JSON. Else encode it.
Further reading on Ajax requests:
https://api.jquery.com/jquery.get/
https://api.jquery.com/jquery.post/
回答2:
This may prove useful: How do I send a cross-domain POST request via JavaScript?
Also, if you do not need to use POST you could use jsonp (no CORS setup required)
回答3:
Your easiest solution here is to enable CORS, assuming you control the page you're trying to access, which you can do in a number of different ways as detailed by that site. This error will also go away if you try and make your AJAX request from the same host as the page your Javascript code is running on--same host in this case means from the same domain (including the same subdomain).
回答4:
There is NO WAY (using XMLHttpRequest), If you have no control to the remote server
< comment me the reason for down vote please.
CORS introduces a standard mechanism that can be used by all browsers for implementing cross-domain requests. The spec defines a set of headers that allow the browser and server to communicate about which requests are (and are not) allowed
Cross-site HTTP requests initiated from within scripts have been subject to well-known restrictions, for well-understood security reasons. For example HTTP Requests made using the XMLHttpRequest object were subject to the same-origin policy. In particular, this meant that a web application using XMLHttpRequest could only make HTTP requests to the domain it was loaded from, and not to other domains.
That's the rule. Even you may find a way to bypass that, it will be fixed some day, simply because that's a violation of the rule
