I'm calling several functions (which I can't edit) in sequence, but some of the functions redirect the user, so I never get to the next one.
I'm calling a third-party function which has calls to wp_redirect() which I'm able to prevent, but then the next line is exit; which I can't figure out how get around.
I was hoping to get around it with the ob_ functions, but no luck so far.
Any suggestions, hacky or otherwise, will be hugely appreciated!
edit: I have an idea I haven't tried yet - somehow spawning off new processes to perform these tasks - what would be best way to do that, waiting for each to complete before moving on.
I believe is possible to get the source code of the php interpreter ... mess with the exit function and then recompile and install on the web server your new custom version of php ...
I'm afraid you just can't. There is an option to redefind native php function, see runkit_function_redefine.
But in the comments it also says:
language constructs
(eval, die, exit, isset, unset, echo etc.) which might be confused
with functions, cannot be renamed or redefined even with
runkit.internal_override.
You may be able to use runkit_function_redefine. You'll need to make sure you can modify internal functions in your php.ini file in order to be able to change native/internal functions.
I think the php.ini setting you need to ensure is switched on is runkit.internal_override.
I've not tested this.
However, since exit is a language construct I'm not even sure it's possible to get around it even with the above function.
In the end I went with using cURL to make three synchronous requests to a file with different GET params.
Throw an exception in wp_redirect, and wrap the code with try-catch statement, then check if the exception message contains the message you have set and return the response accordingly, I have used this hack with most plugins including woocommerce, ultimatemember etc...
example:
ob_start();
try{
whatever code....
}catch(\Exception $e){
}
echo ob_get_clean();
I modified about 600 lines of code amongst over 5000 lines of code by updating function calls to match the new library I created for use with the script. I have spot some errors manually when updating before by hand, but I believe I overlooked some.
So far, the only way I can spot them is to run the code and have it crash when the error happens. This is a bad idea because such errors will happen before resources are freed.
Here's an example in code that explains my question:
Say I have mainline code (called index.php) that consists of this:
<?php
include "library.php";
$file=fopen("afile","w");
doWrite($file);
brokenFunction();
fclose($file);
exit();
?>
and say library.php contains only this:
<?php
function doWrite($file){
fwrite($file,"Test");
doNothing();
}
?>
Because brokenFunction(); and doNothing(); don't exist, an error is expected. Rather than PHP compile then execute code up until the first failing function call, how do I have PHP check to see if all referenced functions the mainline code links to exist before executing code?
So in my example, I expect an error and the code to stop compiling/executing at $file=fopen("afile","w"); because brokenFunction(); and doNothing(); don't exist.
How do I achieve this?
You can use the built-in function_exists() function:
if (!function_exists('brokenFunction')) {
throw new \Exception('brokenFunction is missing');
}
But this will only raise an error when executing the code.
Some tools like PHPStorm can check your code (without running it) and throw warnings if a function is missing.
Some other tools are listed in this (closed) SO question: Is there a static code analyzer [like Lint] for PHP files?.
The best way I've found to globally debug an environment without using #A.L's method and pasting a function_exists call before every edited line, is to use a PHP debugger of some sort, most likely built into an IDE that compares every function call line against a 'test compile' of your code and all included libraries to make sure the called function exists (and would likely underline it in red if it didn't). A PHP IDE like Aptana might be what you're looking for (especially if you see yourself having future updates to run as this solution will have the time overhead of installing/setting up Aptana).
I have found that one common reason for the error is an exception being thrown from within an exception handler. I'm quite sure this doesn't happen in the application I'm trying to debug... But I've put all the initialization processing lines at the top of index.php in a try/catch.*
It can apparently also happen because some things cannot be serialized to be stored in a session. At most this application stores arrays into the session (quite a bit), but I'm confident that it doesn't store anything too out of the ordinary in it.
Someone commented that it happened to them because their primary key needed to be CHAR(32) instead of INT(11). The PK's in this app are all INTs.
Other suggestions are that it could be a problem with PHP 5.3.3 fixed in 5.3.6, full disk, and a need to typecast a SimpleXML value. We do happen to be running PHP 5.3.3, but upgrading would have to be a last resort in this case. It hasn't always been doing this.
UPDATE/NOTE: I actually can't reproduce the error myself, only see it happening in the logs, see below paragraph for where I believe the error is happening...
* From the error logs, it seems likely that at least one place it is happening is index.php. I am deducing this only because it is indicated in some entries by a referring URL. The try/catch code is currently only around the "top" initialization portion of the script, below that is mostly the HTML output. There is some PHP code in the output (pretty straightforward stuff though), so I may need to test that. Here is the catch part, which is not producing any output in the logs:
} catch (Exception $e) {
error_log(get_class($e)." thrown. Message: ".$e->getMessage(). " in " . $e->getFile() . " on line ".$e->getLine());
error_log('Exception trace stack: ' . print_r($e->getTrace(),1));
}
Would really appreciate any tips on this!
EDIT: PHP is running as an Apache module (Server API: Apache 2.0 Handler). I don't think there are any PHP accelerators in use, but it could just be that I don't know how to tell. None of the ones listed on Wikipedia are in phpinfo().
As far as I can tell the MPM is prefork. This is the first I'd ever looked into the MPM:
# ./httpd -l
Compiled in modules:
core.c
prefork.c
http_core.c
mod_so.c
The problem
In short you have a exception thrown somewhere, you have no idea where and up until now you could not reproduce the error: It only happens for some people, but not for you. You know that it happens for other people, because you see that in the error logs.
Reproduce the problem
Since you have already eliminated the common reasons you will need to reproduce the error. If you know which parameter will cause the error it should be easy to locate the error.
Most likely it is enough if you know all the POST/GET parameters.
If you can't reproduce with just these, you need to know additional request headers. Such as user agent, accept-encoding,...
If you still can't reproduce, then it becomes very difficult: The error may depend on a state (a session), the current time, the source ip address or the like.
The custom log method
Let's start simple: To get all parameters you can write in the very beginning of the affected php file something like:
file_put_contents("/path/to/some/custom_error_log", date()."\n".print_r(get_defined_vars(), true), FILE_APPEND | LOCK_EX);
Don't forget that the custom_error_log file must be writable to your php application. Then, when the error occurs in the error log, find the corresponding lines in your custom_error_log file. Hopefully there are not to many requests per second so that you can still identify the request. Maybe some additional parameters in the error log like source ip can help you identify the request (if your error log shows that).
From that data, reconstruct a request with the same POST/GET parameters.
The tcpdump method
The next option that is very simple as well, but requires you to have root-access on your target machine is to install tcpflow. Then create a folder, cd into that folder and simply execute (as root) tcpflow "port 80". The option (port 80) is a pcap filter expression. To see all you can do with that, see man pcap-filter. There is a lot what these filter expressions can do.
Now tcpflow will record all tcp connections on port 80, reconstruct the full data exchange by combining the packages belonging to one connection and dump this data to a file, creating two new files per connection, one for incoming data and one for outgoing data. Now find the files for a connection that caused an error, again based on the timestamp in your error log and by the last modified timestamp of the files. Then you get the full http request headers. You can now reconstruct the HTTP request completely, including setting the same accept-encoding, user-agent, etc. You can even pipe the request directly into netcat, replaying the exact request. Beware though that some arguments like a sessionid might be in your way. If php discovers that a session is expired you may just get a redirect to a login or something else that is unexpected. You may need to exchange things like the session id.
Mocking more things
If none of this helps and you can't reproduce the error on your machine, then you can try to mock everything that is hard to mock. For example the source ip adress. This might make some stunts necessary, but it is possible: You can connect to your server using ssh with the "-w" option, creating a tunnel interface. Then assign the offending ip adress to your own machine and set routes (route add host ) rules to use the tunnel for the specific ip. If you can cable the two computers directly together then you can even do it without the tunnel.
Don't foget to mock the session which should be esiest. You can read all session variables using the method with print_r(get_defined_vars()). Then you need to create a session with exactly the same variables.
Ask the user
Another option would be actually ask the user what he was doing. Maybe you can follow the same steps as he and can reproduce.
If none of this helps
If none of that helps... well... Then it gets seriously difficult. The IP-thing is already highly unlikely. It could be a GEO-IP library that causes the error on IPs from a specific region, but these are all rather unlikely things. If none of the above helped you to reproduce the problem, then you probably just did not find the correct request in all the data generated by the custom_log_file-call / tcpflow. Try to increase your chances by getting a more accurate timestamp. You can use microtime() in php as a replacement for date(). Check your webserver, if you can get something more accurate than seconds in your error log. Write your own implementation of "tail", that gives you a more accurate timestamp,... Reduce the load on the system, so that you don't have to choose from that much data (try another time of day, load of users to different servers,...)
circle the problem once you can reproduce
Now once you can reproduce it should be a walk in the park to find the actual cause. You can find the parameter that causes the error by trial and error or by comparing it to other requests that caused an error, too, looking for similarities. And then you can see what this parameter does, which libraries access it, etc. You can disable every component one by one that uses the parameter until you can't reproduce anymore. Then you got your component and can dive into the problem deeper.
Tell us what you found. I am curious ;-).
I had such an error, too. Found out that I returned a sql object in my session class (that was used by the session_handler) instead of returning nothing or at least not the sql object. First look into your _write and _read methods, if you too return some incorrect stuff.
Notice: ... Unknown on line 0 - How to find correct line, it's NOT "line 0"
I realize this question has already been answered, but I'll add this since it may help someone:
I managed to (unintentionally) produce errors without a stack frame from a function which used its own error handler to maintain control of execution while calling a potentially "dangerous" function, like this:
// Assume the function my_error_handler() has been defined to convert any
// PHP Errors, Warnings, or Notices into Exceptions.
function foo() {
// maintain control if danger() crashes outright:
set_error_handler('my_error_handler');
try {
// Do some stuff.
$r = danger();
} catch (Exception $e) {
$r = 'Bad Stuff, Man!';
}
restore error_handler();
return $r;
}
The "untraceable failure" would happen at the end of the program execution if the logic in "Do some stuff" returned from foo() directly, bypassing the call to restore_error_handler(). What I took away from the experience is this:
PHP maintains a stack of error handlers which gets deeper/taller with each call to set_error_handler().
Bad Stuff can happen if you push error handlers onto the stack and don't clean up after yourself before the program exits "normally".
This was a tough bug to isolate - I basically narrowed the problem down to the above function and then stared at it until my eyes bled.
So how would I have tracked this down, knowing what I know now? Since I don't know of any way to inspect the PHP error handler "stack" directly, I'm thinking it might make sense to use a Singleton object to encapsulate all set/restore operations for PHP error handlers. At least then it would be possible to inspect the state of the Singleton before exiting the program normally, and if "dangling" error handlers are detected to generate a sensible failure/warning message before PHP freaks out.
Instead of wrapping code in a try/catch block, what happens when you register an exception handler? Clearly your try/catch block is not catching the exception, thus resulting in the errors logged to Apache. By registering a handler, you can be sure any uncaught exception is handled.
Also, if you're using namespaces in your application, make sure you write \Exception in your catch block (or include the Exception class via a use statement).
This may be a little late but one issue I discovered when moving a site from a local to a remote server. I was using Concrete5 cms had developed my site locally(windows 8 in xampp) and then uploaded to a remote server running Cent 0S
Windows mysql by default is case insensitive and created a lower case database. Once this was uploaded to the remote server I received the "Exception thrown without a stack frame in Unknown on line 0?"
I then corrected the database tables case and my site started working again.
For us, this error was due to inadvertently serializing SimpleXML objects.
If you are using SimpleXML objects with 5.3.3, make sure you are are casting the node values to whatever you need (e.g. string) if you are serializing the values in the session.
Before:
$token = $response->Token->Value;
/* token saved in session, results in line 0 error */
After:
$token = (string) $response->Token->Value;
/* token saved in session, no error */
I had completely the same error. A very spacial case: if you connect an unnamed function (closure) hook to an object instance's hook point. After that you try to serialize this object.
I had the same error after filling the Illuminate Eloquent model's Fillable property incorrectly. Note the last 3 elements of the array, one is missing a coma.
protected $fillable = [
'budget',
'routestatus' ,
'userroutenumber'
'totalmovingseconds',
'totalidleseconds'
];
I had the same error, it appeared upgrading server from centos 5 to centos 6 and downgrading PHP from 5.4 to 5.3. Actual issue was PHP apc, not configured properly. Check your APC. I was using Symfony2, so you might find some help at Symfony Unable to allocate memory for pool
one simple way to produce this error is an old server with register_globals = On. then you only need two lines of code:
<?php
$_SESSION["my_var"] = "string";
$my_var = new MyClass(); //could be any class, i guess
?>
as soon as you reload this page once, you'll get the Exception thrown without a stack frame in Unknown on line 0 - error. seems like there is a conflict between the instance of the class and the (session) variable.
at least this is how i got this annoying error which is so hard to debug.
This problem occurred for me when I changed the namespace on a few Symfony bundles. Deleting the files in the the symfony cache directory fixed the issue.
Likely you have a corrupt/inconsistent table in the database. Try dumping the database. If you get a error that's the time. Repair that table and the issue should go away.
It is for this reason why clean install works. The clean install is just that clean.
mysqlcheck should work but if it does not show and issue still do above.
Is there a way to have PHP log errors to a file or email me errors INCLUDING $_POST[] & $_GET[] and $_SERVER[] data?
Right now I get a log of PHP FATAL and WARNING errors and 404 NOT_FOUND errors but it's hard to debug some errors without knowing things like user input and the referrer.
Thanks
error_log(print_r($_POST, true));
error_log(print_r($_GET, true));
Put that into a custom error handler and it'll log both for you (the 'true' parameter makes print_r return text instead of outputting it).
You might need to boost the max line length in the error log with log_errors_max_len, as it defaults to 1024 chars and will truncate everything after that (it won't split >1024 char data across multiple lines).
If you are using PHP 5 create a custom exception class which will extend the native PHP Exception class and add whatever data collecting / logging methods you like. That way you could easily combine try {} catch() {} block with Exceptions and have your own way of controlling how you want to log all data.
I would recommend the error_log() function. I use that a lot to debug stuff in php.
http://php.net/manual/en/function.error-log.php
I worked on a telecom project that used CI to handle a Felx based frontend, we hijacked all possible error reporting and wrote a wrapper on syslog functions and used it in our application, the result was we could log whatever data we wanted and the log was visible through system log viewer :-)
I'am building simple Ajax application (via jquery). I have strange issue. I found where the problem is, but I don't know how to solve it.
This is simple server-side php code:
<?php
require('some.php');
$return['pageContent'] = 'test';
echo(json_encode($return));
?>
On the client side, the error "Invalid JSON" is thrown.
I have discovered that if I delete require function, everything work fine.
Just for information, the "some.php" is an empty php file. There is no error when I open direct php files.
So, conclusion: I cant use require or include function if I want to use ajax?
Use Firebug to see what you're actually getting back during the AJAX call. My guess is that there's a PHP error somewhere, so you're getting more than just JSON back from the call (Firebug will show you that). As for your conclusion: using include/require by itself has absolutely no effect on the AJAX call (assuming there are no errors).
Try changing:
<?php
require('some.php');
$return['pageContent'] = 'test';
echo(json_encode($return));
?>
To:
<?php
$return = array(
'pageContent' => 'test'
);
echo json_encode($return);
?>
The problem might have to do with $return not being declared as an array prior to use.
Edit: Alright, so that might not be the problem at all. But! What might be happening is you might be echoing out something in the response. For example, if you have an error echoing out prior to the JSON, you'd be unable to parse it on the client.
if the "some.php" is an empty php file, why do you require it at all?!
require function throws a fatal error if it could't require the file. try using include function instead and see what happens, if it works then you probably have a problem with require 'some.php';
A require call won't have any effect. You need to check your returned output in Firebug. If using Chrome there is a plugin called Simple REST Client. https://chrome.google.com/extensions/detail/fhjcajmcbmldlhcimfajhfbgofnpcjmb through which you can quickly query for stuff.
Also, it's always good to send back proper HTTP headers with your response showing the response type.
It's most likely the BOM as has been discussed above. I had the same problem multiple times and used Fiddler to check the file in hex and noticed an extra 3 bytes that didn't exist in a prior backup and in new files I created. Somehow my original files were getting modified by Textpad (both in Windows). Although when I created them in Notepad++ I was fine.
So make sure that you have your encoding and codepages set up properly when you create, edit, and save your files in addition to keeping that consistent across OSes if you're developing on windows let's say and publishing to a linux environment at your hosting provider.