I have an old application witch pops up an error at a certain location. The error is about an wrong set variable. Only from the error it is not possible to find the location where the variable is set wrong. Now my idea is to use reflections to find the location.
Is it possible to use reflections to find the code position at which a variable gets a certain value?
The idea: I have the name and the value of the variable. Now if both are matching a certain event should be triggered and echo the actual parsed file and line number.
Every ideas that help are appreciated.
Thank you,
-lony
P.S.: Is it possible even if the application is not really object oriented and uses a lot of spaghetti code?
I would be you do a debug_backtrace at the point where the error occurs and try to exploit the stack trace to see where the variable is changed. The debug_backtrace would give you a list of file included after it should be fairly easy to filter a list of line with a global search (i.e. grep)
var_dump(debug_backtrace())
if (variable == value) {
echo "variable equals value, line #whatever"+"<br/>";
}
Just place these at various points in code and see which ones display. Manually enter line numbers.
I found a solution to one of my problems.
The function debug_print_backtrace helped me finally debugging my spaghetti code. I found it by reading this post.
-Cheers
Related
I have a universal function that I use for processing SQL. I am getting this error (just a few times a day, not frequently).
PHP Catchable fatal error: Object of class PDO could not be converted to string in...
Basically, an array of values is passed for a function that I am using, and I must have slipped up in my code and placed a PDO object in that array.
I need to make an array_filter function that checks if the variable is a PDO object. How do I do a simple if statement for this?
if($var == PDO)
Edit: Thanks for the great answers! In case anyone is interested, here is how I solved the problem. I was able to find where the invalid input was coming from.
$before=$original_array;
$after = array_filter($before, "find_error");
if(count($before)!=count($after)){
$error=print_r(debug_backtrace(false),true);
$arr=print_r($before,true);
send_message("admin#email.com","Error Report",$arr.$error);
//send_message is a simple function for sending emails. You could also write information to a txt file, etc.
}
function find_error($var){
return !($var instanceof PDO);
}
instanceof is used to determine whether a PHP variable is an instantiated object of a certain class:
if($var instanceof PDO) {
// your code
}
You can use instanceof for this.
if($var instanceof PDO){
//code here
}
However you say
I must have slipped up in my code and placed a PDO object in that array
I would recommend that you find and correct that slip up, otherwise you may be storing other problems for yourself as you continue development and possibly pass that array to other parts of your application.
Always cure the problem, rather than focusing on treating a symptom.
You are trying to cure the symptom instead of disease.
You are trying it out of mere speculation.
What are you trying to do is called "error message suppression". With desired if statement, already brought to you by good Samaritans, you're just closing your eyes pretending that there is no error in the program flow. While it remains.
A good programmer have to ask "how to track down the error and how to fix it", not "how to gag it".
So, you have to use debug_backtrace() to track the place where wrong data were added. this function have to be placed in the line marked by the error message you have.
Then you need to debug the code to make sure that your assumption of adding PDO result is right.
And finally fix the error.
It seems you managed to solve the problem the right way while I was writing this answer. But I got to leave it here for the future readers.
Is it possible to parse the contents of a constant in PHP?
For example,
define('WHO_AM_I', 'My name is $_SESSION['who_am_i'].'); // setup the constant string
echo eval(WHO_AM_I); // something like this -- but the eval() returns an error
Please note that I do not know the value of the _SESSION var until I actually use the constant later in the script stream.
Thanks.
AMENDED WITH REASON FOR WANTING TO DO THIS
I want to pull "hard coding" out of my script and give the user the ability to configure certain taxonomy in their site. So while I was doing this I also wanted to create a quasi-dynamic constant that I thought I might be able to parse later in the script.
If it can't be done...then it can't be done.
Don't shoot me for asking the question though.
A FINAL COMMENT TO AVOID ALL THIS CONFUSION
The purpose of my question has nothing to do with the eval() function. I am actually regretting having put it in there in the first place.
I put the eval() in the question simply to demonstrate to stackoverflow members that I did a bit if prep on my question rather than asking an open ended -- hey give me a solution without having offered any stab at it myself. So please disregard the eval().
All I want to know is can I somehow craft a define() in an way that makes the assigned value parse-able later in my script. That's it, that's all.
AMENDMENT C
I know I can do the following although I don't want to do it this way:
define('PARSE_ABLE_CONSTANT_PART_A', 'My name is ');
define('PARSE_ABLE_CONSTANT_PART_B', '.');
...later down the script road...
echo PARSE_ABLE_CONSTANT_PART_A . $_SESSION['who_am_i'] . PARSE_ABLE_CONSTANT_PART_B;
I just don't want to do it this way if I can make it slicker using an embedded var in the constant.
This seems really fishy, as other users have pointed out. You could do something like this if you wanted:
define('WHO_AM_I', 'echo \'My name is \'.$_SESSION[\'who_am_i\'];');
eval(WHO_AM_I);
This will always just echo the variable. You need to eval an expression afaik.
Just read your edit. I think you would be better suited with an .ini file, or maybe a static class with static properties. Makes it much more flexible, and you avoid the eval. You are talking user-generated content from what I can see - subjecting that to an eval call seems highly insecure.
A quick example of a static class you could use:
<?php
class myConstants{
public static function _($key){
switch($key){
case "WHO_AM_I":
return "My name is ".$_SESSION['who_am_i'];
break;
case "OTHER_CONSTANT":
// does some other evaluation and returns a string
break;
}
throw new Exception("Constant isn't defined");
}
}
?>
Then you can just echo myConstants::_('WHO_AM_I');
Constants by definition don't allow you to set it with dynamic content.
Here is a quote from the php manual:
As the name suggests, that value cannot change during the execution
of the script
You can see more by going here
You might be thinking of magical constants
Let's say that at the beginning of a random function variable $variables['content'] is 1,000 characters long.
This random function is very long, with many nested functions within.
At the end of the function $variables['content'] is only 20 characters long.
How do you find which of nested functions modified this variable?
Not sure how you'd want to return it but you could use the magic constant __LINE__. That returns the line of the current document.
You could create a variable called $variables['line'] and assign __LINE__ as the value, where appropriate.
If it were me, first I'd consider breaking apart the 1000-line beast. There's probably no good reason for it to be so huge. Yes, it'll take longer than just trying to monkey-patch your current bug, but you'll probably find dozens more bugs in that function just trying to break it apart.
Lecture over, I'd do a search/replace for $variables['content'].*=([^;]*); to a method call like this: $variables['content'] = hello(\1, __LINE__);. This will fail if you are assigning strings with semicolons in them or something similar, so make sure you inspect every change carefully. Write a hello() function that takes two parameters: whatever it is you're assigning to $variables['content'] and the line number. In hello(), simply print your line number to the log or standard error or whatever is most convenient, and then return the first argument unchanged.
When you're done fixing it all up, you can either remove all those silly logging functions, or you can see if 'setting the $variables['content'] action' is important enough to have its own function that does something useful. Refactoring can start small. :)
I think this is a problem code tracing can help with.
In my case I had this variable that was being modified across many functions, and I didn't know where.
The problem is that at some point in the program the variable (a string) was around 40,000 characters, then at the end of the program something had cut it to 20 characters.
To find this information I stepped through the code with the Zend debugger. I found the information I wanted (what functions modified the variable), but it took me a while.
Apparently XDebug does tell you what line numbers, in what functions the variables are modified:
Example, tracing documentation, project home, tutorial article.
I am dealing with a very strange situation that has to do with the Warning: Cannot use a scalar value as an array and memory leak.
The script is very simple and I can not figure out the problem.
Code
$variants=array();
if($text)
{
$v=explode(",",$text);
if(is_array($v) && sizeof($v)>0)
{
foreach($v as $i=>$part)
{
$tmp=explode(":",$part);
list($thekey,$thevalue)=$tmp;
//$variants=array();
echo "<div>TYPE==".gettype($variants)."</div>";
echo $variants[$tmp[0]]=$tmp[1];
}
}
}
If I run the code above as stand alone is working fine. But when put it in my framework as small part behave very strange. I got a Warning: Cannot use a scalar value as an array and in order to solve it I added
$variants=array();
on the first line. When running the script the gettype returns ��� the first time and after that return integer.
If i uncomment $variants=array(); just before the gettype, it works. But of course I don't to get the whole array, only the last record return.
I parse my code to find out that the variables I use are declared before I even change all the variable names to stupids but no luck.
Trying to debug and tune the code where times that when running the script instead of see something in the screen the browser download the script instead and some other times I had memory leaks.
Can anyone point where or what to look for, or debug it and solve it?
Problem solved
Before run the code i was calling a function
$obj->draw($$id)
That was causing the problem
The solution
$value=$$id;
$obj->draw($value)
I dont know why this causing the problem.
If anyone has a theory please post it.
I'm currently working on a very large project, and am under a lot of pressure to finish it soon, and I'm having a serious problem. The programmer who wrote this last defined variables in a very odd way - the config variables aren't all in the same file, they're spread out across the entire project of over 500 files and 100k+ lines of code, and I'm having a hell of a time figuring out where a certain variable is, so I can fix an issue.
Is there a way to track this variable down? I believe he's using SMARTY (Which I can not stand, due to issues like this), and the variable is a template variable. I'm fairly sure that the variable I'm looking for was initially defined as a PHP variable, then that variable is passed into SMARTY, so I'd like to track down the PHP one, however if that's impossible - how can I track down where he defined the variable for SMARTY?
P.S. I'm in Vista, and don't have ssh access to the server, so 'grep' is out of the question.
Brute force way, because sometimes smarty variables are not directly assigned, but their names can be stored in variables, concatenated from many strings or be result of some functions, that makes it impossible to find in files by simply searching / greping.
Firstly, write your own function to print readable backtrace, ie:
function print_backtrace()
{
$backtrace = debug_backtrace(FALSE);
foreach($backtrace as $trace)
echo "{$trace['file']} :: {$trace['line']}<br>";
}
Open main smarty file (Smarty.class.php by default) and around line 580 there is function called assign. Modify it to watch for desired variable name:
function assign($tpl_var, $value = null)
{
if($tpl_var == 'FOOBAR') /* Searching for FOOBAR */
{
print_backtrace();
exit;
}
The same modification may be required for second function - assign_by_ref. Now after running script you should have output like that:
D:\www\test_proj\libs\smarty\Smarty.class.php :: 584
D:\www\test_proj\classes.php :: 11
D:\www\test_proj\classes.php :: 6
D:\www\test_proj\functions.php :: 7
D:\www\test_proj\index.php :: 100
Second line points to the place where variable was first assigned.
This sort of thing is the #1 reason I install Cygwin on all my windows machines.
grep myvariablename `find project_dir -name "*.php"`
I can't imagine programming without a working grep.
There is an interesting further option, ugly like hell but helpful if you are really lost.
If you would like to know where THE_NAME was defined, write lines like these on a place you are sure is run first:
error_reporting(E_ALL);
define('THE_NAME', 'Chuck Norris');
If later PHP will run the definition you are looking for, it will write a notice like this:
Notice: Constant THE_NAME already defined
in /home/there/can-rip-a-page-out-of-facebook.com/SomeConfiguration.php on line 89
Then you know that the definition you are looking for is in the file SomeConfiguration.php on line 89.
To have this working, you must consider
if there are HTTP forwards in the framework on the way to the code you set in
if there are further commands setting the PHP error reporting mode
So sometimes it helps to add some exit('here') in order not to blur the output. Maybe you have to narrow down a bit or you have to set error_reporting earlier, but you'll find it.
It's not a perfect solution, but I find agent ransack useful for searching large directories and files. Might help you narrow things down. The search results will allow you to read the exact line it finds a match on in the result pane.
If you use the netbeans editor just "right click" -> "go to Definition"
Or ctrl + click on the variable.
If the editor can't figure it out, you could fallback to the "Find in files" option.
Just use one of the available PHP IDEs (or a simple text editor like Notepad++ if you're really desperate) and search for the name of the variable in all source files (most PHP IDEs also support finding where functions/vars were defined and allow you to jump to the relevant piece of code). Though it seems weird that you don't know what piece of code calls the template (whether it's Smarty or anything else doesn't really matter). You should be able to drill down in the code starting from the URI (using any IDE which supports debugging), because that way you're bound to see where said variable is defined.