Retrieve HTTP POST variables using multipart/form-data sent from an iOS device

Question

I need to retrieve the POST variables being sent from my iOS application, but so far I have had no luck. Here is some background:

I have an iOS application that posts an image along with some variables to a php page that simply saves the variables in a file (for debugging) and moves the image to the current directory (server side). I can get a handle on the image without issue using the $_FILE variable, however I cannot seem to get any of the POST parameters at all.

Some general info and what I've tried:

Tried getting post variables with $_POST, then dumped $_POST...it was empty
Tried dumping $HTTP_RAW_POST_DATA (though this page says it's not populated when using multipart/form-data)
Checked the "post_max_size" variable (it's 8MB, I'm sending in the KB range) after seeing this post
Used wireshark to verify that the variables are indeed being received by the server

I'm using modified sample code from here

// create request
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
[request setCachePolicy:NSURLRequestReloadIgnoringLocalCacheData];
[request setHTTPShouldHandleCookies:NO];
[request setTimeoutInterval:30];
[request setHTTPMethod:@"POST"];

NSMutableDictionary* _params = [[NSMutableDictionary alloc] init];
[_params setObject:@"1.0" forKey:@"ver"];
[_params setObject:@"en" forKey:@"lan"];
[_params setObject:[NSString stringWithFormat:@"%@", @"myUserName"] forKey:@"userId"];

// the boundary string : a random string, that will not repeat in post data, to separate post data fields.
NSString *BoundaryConstant = @"V2ymHFg03ehbqgZCaKO6jy";

// string constant for the post parameter 'file'
NSString *FileParamConstant = @"media";

//Setup request URL
NSURL *requestURL = [[NSURL alloc] initWithString:@"http://myWebAddress/myAction.php"];

// set Content-Type in HTTP header
NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@", BoundaryConstant];
[request setValue:contentType forHTTPHeaderField: @"Content-Type"];

// post body
NSMutableData *body = [NSMutableData data];

// add params (all params are strings)
for (NSString *param in _params) {
    [body appendData:[[NSString stringWithFormat:@"--%@\r\n", BoundaryConstant] dataUsingEncoding:NSUTF8StringEncoding]];
    [body appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"%@\"\r\n\r\n", param] dataUsingEncoding:NSUTF8StringEncoding]];
    [body appendData:[[NSString stringWithFormat:@"%@\r\n", [_params objectForKey:param]] dataUsingEncoding:NSUTF8StringEncoding]];
}

// add image data
NSData *imageData = UIImageJPEGRepresentation([self.imageButtonOutlet backgroundImageForState:UIControlStateNormal], 1.0);
if (imageData) {
    printf("appending image data\n");
    [body appendData:[[NSString stringWithFormat:@"--%@\r\n", BoundaryConstant] dataUsingEncoding:NSUTF8StringEncoding]];
    [body appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\'%@\'; filename=\"image.jpg\"\r\n", FileParamConstant] dataUsingEncoding:NSUTF8StringEncoding]];
    [body appendData:[@"Content-Type: image/jpeg\r\n\r\n" dataUsingEncoding:NSUTF8StringEncoding]];
    [body appendData:imageData];
    [body appendData:[[NSString stringWithFormat:@"\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
}

[body appendData:[[NSString stringWithFormat:@"--%@--\r\n", BoundaryConstant] dataUsingEncoding:NSUTF8StringEncoding]];

// setting the body of the post to the reqeust
[request setHTTPBody:body];

// set the content-length
NSString *postLength = [NSString stringWithFormat:@"%d", [body length]];
[request setValue:postLength forHTTPHeaderField:@"Content-Length"];

// set URL
[request setURL:requestURL];

NSURLConnection *postConnection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
[postConnection start];
[postConnection release];

Also, here is myAction.php, as it stands right now:

<?php

$fp_file = fopen("./output_files.txt", "w");
$fp_post = fopen("./output_post.txt", "w");

$post_content = var_export($_POST , TRUE);
$file_content = var_export($_FILES, TRUE);
fwrite($fp_file, $file_content);
fwrite($fp_post, $post_content);


fclose($fp_file);
fclose($fp_post);

move_uploaded_file( $_FILES['media']['tmp_name'], "test.jpg");

?>

score 1 · Accepted Answer · answered Apr 11 '13 at 21:44

After 4 hours of debugging, the problem was in my php code... which has been edited to reflect the change. the variable $post_content was created with the name $post_contnet. Hopefully this will at lease serve as code guide to others trying to implement a similar service.

You can't fix stupid.

score 0 · Answer 2 · answered Apr 11 '13 at 19:20

0

Is there any reason for implementing the HTTP protocol yourself?

There are several networking packages out there

https://github.com/AFNetworking/AFNetworking

supports multi-part form data I believe.

answered Apr 11 '13 at 19:20

yc.lin

379
1
6

score 0 · Answer 3 · answered Apr 12 '13 at 04:41

use following code to upload i have made change only at last line of this function, you can set delegates for NSURLConnection according to your requirement.

-(void)upload
{
    // create request
    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
    [request setCachePolicy:NSURLRequestReloadIgnoringLocalCacheData];
    [request setHTTPShouldHandleCookies:NO];
    [request setTimeoutInterval:30];
    [request setHTTPMethod:@"POST"];

    NSMutableDictionary* _params = [[NSMutableDictionary alloc] init];
    [_params setObject:@"1.0" forKey:@"ver"];
    [_params setObject:@"en" forKey:@"lan"];
    [_params setObject:[NSString stringWithFormat:@"%@", @"myUserName"] forKey:@"userId"];

    // the boundary string : a random string, that will not repeat in post data, to separate post data fields.
    NSString *BoundaryConstant = @"V2ymHFg03ehbqgZCaKO6jy";

    // string constant for the post parameter 'file'
    NSString *FileParamConstant = @"media";

    //Setup request URL
    NSURL *requestURL = [[NSURL alloc] initWithString:@"http://myWebAddress/myAction.php"];

    // set Content-Type in HTTP header
    NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@", BoundaryConstant];
    [request setValue:contentType forHTTPHeaderField: @"Content-Type"];

    // post body
    NSMutableData *body = [NSMutableData data];

    // add params (all params are strings)
    for (NSString *param in _params) {
        [body appendData:[[NSString stringWithFormat:@"--%@\r\n", BoundaryConstant] dataUsingEncoding:NSUTF8StringEncoding]];
        [body appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"%@\"\r\n\r\n", param] dataUsingEncoding:NSUTF8StringEncoding]];
        [body appendData:[[NSString stringWithFormat:@"%@\r\n", [_params objectForKey:param]] dataUsingEncoding:NSUTF8StringEncoding]];
    }

    // add image data
    NSData *imageData = UIImageJPEGRepresentation([self.imageButtonOutlet backgroundImageForState:UIControlStateNormal], 1.0);
    if (imageData) {
        printf("appending image data\n");
        [body appendData:[[NSString stringWithFormat:@"--%@\r\n", BoundaryConstant] dataUsingEncoding:NSUTF8StringEncoding]];
        [body appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\'%@\'; filename=\"image.jpg\"\r\n", FileParamConstant] dataUsingEncoding:NSUTF8StringEncoding]];
        [body appendData:[@"Content-Type: image/jpeg\r\n\r\n" dataUsingEncoding:NSUTF8StringEncoding]];
        [body appendData:imageData];
        [body appendData:[[NSString stringWithFormat:@"\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
    }

    [body appendData:[[NSString stringWithFormat:@"--%@--\r\n", BoundaryConstant] dataUsingEncoding:NSUTF8StringEncoding]];

    // setting the body of the post to the reqeust
    [request setHTTPBody:body];

    // set the content-length
    NSString *postLength = [NSString stringWithFormat:@"%d", [body length]];
    [request setValue:postLength forHTTPHeaderField:@"Content-Length"];

    // set URL
    [request setURL:requestURL];

    NSURLResponse *response = nil;
    NSError *err = nil;
    NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&err];
    NSString *str = [[NSString alloc] initWithBytes:[data bytes] length:[data length] encoding:NSUTF8StringEncoding];
    NSLog(@"Response : %@",str);
}

and in myAction.php file write following PHP code to read your parameters

<?php
    echo "FileType :". $_FILES["media"]["type"] ;
    echo "FileName :". $_FILES["media"]["name"] ;
    echo "FileSize :".($_FILES["media"]["size"] / 1024)/100 ;
    echo "Version :".$_REQUEST["ver"];
    echo "Language :".$_REQUEST["lan"];
?>

Retrieve HTTP POST variables using multipart/form-data sent from an iOS device

3 Answers3