PHP - Debugging Curl

Question

I'd like to see what the post fields in the request are before I send it. (For debugging purposes).

The PHP library (class) I am using is already made (not by me), so I am trying to understand it.

As far as I can tell, it uses curl_setopt() to set different options like headers and such and then it uses curl_exec() to send the request.

Ideas on how to see what post fields are being sent?

See also How to display request headers with command line curl. — Vadzim
– Vadzim, Commented Oct 9, 2013 at 6:26

hakre · Accepted Answer · 2022-07-04 09:08:02Z

492

You can enable the CURLOPT_VERBOSE option^{Curl, PHP} and log that information to a (temporary) CURLOPT_STDERR:

// CURLOPT_VERBOSE: TRUE to output verbose information.
// Writes output to STDERR, 
// -or- the file specified using CURLOPT_STDERR.
curl_setopt($curlHandle, CURLOPT_VERBOSE, true);

$streamVerboseHandle = fopen('php://temp', 'w+');
curl_setopt($curlHandle, CURLOPT_STDERR, $streamVerboseHandle);

You can then read it after curl has done the request:

$result = curl_exec($curlHandle);
if ($result === FALSE) {
    printf("cUrl error (#%d): %s<br>\n",
           curl_errno($curlHandle),
           htmlspecialchars(curl_error($curlHandle)))
           ;
}

rewind($streamVerboseHandle);
$verboseLog = stream_get_contents($streamVerboseHandle);

echo "cUrl verbose information:\n", 
     "<pre>", htmlspecialchars($verboseLog), "</pre>\n";

(I originally answered similar but more extended in a related question.)

More information like metrics about the last request is available via curl_getinfo. This information can be useful for debugging curl requests, too. A usage example, I would normally wrap that into a function:

$version = curl_version();
extract(curl_getinfo($curlHandle));
$metrics = <<<EOD
URL....: $url
Code...: $http_code ($redirect_count redirect(s) in $redirect_time secs)
Content: $content_type Size: $download_content_length (Own: $size_download) Filetime: $filetime
Time...: $total_time Start @ $starttransfer_time (DNS: $namelookup_time Connect: $connect_time Request: $pretransfer_time)
Speed..: Down: $speed_download (avg.) Up: $speed_upload (avg.)
Curl...: v{$version['version']}
EOD;

edited Jul 4, 2022 at 9:08

answered Jan 21, 2013 at 10:41

hakre

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7 Comments

iisisrael Over a year ago

fopen option should be 'w+'

hakre Over a year ago

@iisisrael: You are right. Corrected. Thanks for the hint.

TheSatinKnight Over a year ago

Before you jump into debugging, however: Try checking the apache log in case an error was tossed (like curl php not being installed, so the function failed!)

Marco Sulla Over a year ago

Thank you. Unluckily, it does not log all the content of the a POST, as curl -v does.

hakre Over a year ago

@MarcoSulla: This is perhaps a different curl version? Compare curl --version and php -i | grep -i curl.

|

JamesG · Accepted Answer · 2017-02-28 23:14:04Z

198

You can enable the CURLOPT_VERBOSE option:

curl_setopt($curlhandle, CURLOPT_VERBOSE, true);

When CURLOPT_VERBOSE is set, output is written to STDERR or the file specified using CURLOPT_STDERR. The output is very informative.

You can also use tcpdump or wireshark to watch the network traffic.

edited Feb 28, 2017 at 23:14

JamesG

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answered Sep 21, 2010 at 12:35

netom

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3 Comments

Mike Over a year ago

It is worth noting that this will not work if you have set CURLINFO_HEADER_OUT to TRUE. So far as I can tell...

Galina Bublik Over a year ago

Than work $info = curl_getinfo($curlhandle); - This comment for myself)

hakre Over a year ago

tcpdump/wireshark ftw.

Mario S · Accepted Answer · 2014-11-16 15:14:17Z

77

Here is a simpler code for the same:

   curl_setopt($ch, CURLOPT_VERBOSE, 1);
   curl_setopt($ch, CURLOPT_STDERR, $fp);

where $fp is a file handle to output errors. For example:

   $fp = fopen(dirname(__FILE__).'/errorlog.txt', 'w');

( Read on http://curl.haxx.se/mail/curlphp-2008-03/0064.html )

edited Nov 16, 2014 at 15:14

answered Oct 28, 2014 at 15:10

Mario S

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1 Comment

Jono Over a year ago

I would have liked to use the answer of @Michaël-R- but I didnt get verbose in the PHP log. Logging to a new file like this worked tho.

Sir l33tname · Accepted Answer · 2016-04-17 09:20:50Z

33

Here is an even simplier way, by writing directly to php error output

curl_setopt($curl, CURLOPT_VERBOSE, true);
curl_setopt($curl, CURLOPT_STDERR, fopen('php://stderr', 'w'));

edited Apr 17, 2016 at 9:20

Sir l33tname

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answered Feb 12, 2016 at 13:17

Michaël R

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Comments

Andrew · Accepted Answer · 2017-02-10 11:25:22Z

33

To just get the info of a CURL request do this:

$response = curl_exec($ch);

$info = curl_getinfo($ch);
var_dump($info);

answered Feb 10, 2017 at 11:25

Andrew

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1 Comment

girorme Over a year ago

For "after" response the curl_getinfo its excelent but for malformed urls for example the getinfo returns non info, the opt CURLOPT_VERBOSE its a better for example

Nick Spicer · Accepted Answer · 2020-01-10 11:19:40Z

11

If you just want a very quick way to debug the result:

$ch = curl_init();
curl_exec($ch);
$curl_error = curl_error($ch);
echo "<script>console.log($curl_error);</script>"

answered Jan 10, 2020 at 11:19

Nick Spicer

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Comments

Serhii Andriichuk · Accepted Answer · 2019-06-24 18:18:08Z

Output debug info to STDERR:

$curlHandler = curl_init();

curl_setopt_array($curlHandler, [
    CURLOPT_URL => 'https://postman-echo.com/get?foo=bar',
    CURLOPT_RETURNTRANSFER => true,

    /**
     * Specify debug option
     */
    CURLOPT_VERBOSE => true,
]);

curl_exec($curlHandler);

curl_close($curlHandler);

Output debug info to file:

$curlHandler = curl_init();

curl_setopt_array($curlHandler, [
    CURLOPT_URL => 'https://postman-echo.com/get?foo=bar',
    CURLOPT_RETURNTRANSFER => true,

    /**
     * Specify debug option.
     */
    CURLOPT_VERBOSE => true,

    /**
     * Specify log file.
     * Make sure that the folder is writable.
     */
    CURLOPT_STDERR => fopen('./curl.log', 'w+'),
]);

curl_exec($curlHandler);

curl_close($curlHandler);

See https://github.com/andriichuk/php-curl-cookbook#debug-request

mario · Accepted Answer · 2018-12-23 20:59:17Z

1

Another (crude) option is to utilize netcat for dumping the full request:

nc -l -p 8000 -w 3 | tee curldbg.txt

And of course sending the failing request to it:

curl_setup(CURLOPT_URL, "http://localhost/testytest");

Notably that will always hang+fail, since netcat won't ever construct a valid HTTP response. It's really just for inspecting what really got sent. The better option, of course, is using a http request debugging service.

answered Dec 23, 2018 at 20:59

mario

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Comments

vee · Accepted Answer · 2025-05-08 16:25:13Z

For PHP 8.4+ you can use the option CURLOPT_DEBUGFUNCTION. See document here.

Example:

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, 'http://yourdomain');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);// this is not required.
curl_setopt($ch, CURLOPT_VERBOSE, true);


$verboseLog = '';

curl_setopt($ch, CURLOPT_DEBUGFUNCTION, 
    function($curlHandle, $type, $data) use (&$verboseLog)
    {
    switch ($type) {
        case CURLINFO_TEXT:
            $verboseLog .= '(informational text)';
            break;
        case CURLINFO_HEADER_IN:
            $verboseLog .= '(response headers)';
            break;
        case CURLINFO_HEADER_OUT:
            $verboseLog .= '(request headers)';
            break;
        case CURLINFO_DATA_IN:
            $verboseLog .= '(response data)';
            break;
        case CURLINFO_DATA_OUT:
            $verboseLog .= '(request data)';
            break;
        case CURLINFO_SSL_DATA_IN:
            $verboseLog .= '(response SSL data)';
            break;
        case CURLINFO_SSL_DATA_OUT:
            $verboseLog .= '(request SSL data)';
            break;
        default:
            $verboseLog .= '(unknown type ' . $type . ')';
            break;
    }
    $verboseLog .= ' ';
    $verboseLog .= var_export($data, true) . PHP_EOL;
});

$result = curl_exec($ch);

curl_close($ch);


var_dump($result);
var_dump($verboseLog);

You can format verbose message in the option CURLOPT_DEBUGFUNCTION. For more info about why verbose with fopen() show nothing, please read this answer.

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