Is there a way to immediately stop PHP code execution?
I am aware of exit but it clearly states:
Terminates execution of the script. Shutdown functions and object destructors will always be executed even if exit is called.
So what I want to achieve is to stop the PHP code execution exactly when I call exit or whatever.
Any help?
Edit: After Jenson's answer
Trial 1:
function newExit() {
__halt_compiler();
}
echo "start";
newExit();
echo "you should not see this";
Shows Fatal error: __HALT_COMPILER() can only be used from the outermost scope in which was pretty expected.
Trial 2:
function newExit() {
include 'e.php';
}
echo "start";
newExit();
echo "you should not see this";
e.php just contains __halt_compiler();
This shows startyou should not see this
Edit: Why I want to do this?
I am working on an application that includes a proprietary library (required through virtual host config file to which I don't have access) that comes as encrypted code. Is a sort of monitoring library for security purpose. One of it's behaviours is that it registers some shutdown functions that log the instance status (it saves stats to a database)
What I want to do is to disable this logging for some specific conditions based on (remote IP)
Please see the following information from user Pekka 웃
According to the manual, destructors are executed even if the script gets terminated using die() or exit():
The destructor will be called even if script execution is stopped using exit(). Calling exit() in a destructor will prevent the remaining shutdown routines from executing.
According to this PHP: destructor vs register_shutdown_function, the destructor does not get executed when PHP's execution time limit is reached (Confirmed on Apache 2, PHP 5.2 on Windows 7).
The destructor also does not get executed when the script terminates because the memory limit was reached. (Just tested)
The destructor does get executed on fatal errors (Just tested) Update: The OP can't confirm this - there seem to be fatal errors where things are different
It does not get executed on parse errors (because the whole script won't be interpreted)
The destructor will certainly not be executed if the server process crashes or some other exception out of PHP's control occurs.
Referenced in this question
Are there any instances when the destructor in PHP is NOT called?
whats wrong with return ?
echo "you will see this";
return;
echo "you will not see this";
You can use __halt_compiler function which will Halt the compiler execution
http://www.php.net/manual/en/function.halt-compiler.php
You could try to kill the PHP process:
exec('kill -9 ' . getmypid());
Apart from the obvious die() and exit(), this also works:
<?php
echo "start";
__halt_compiler();
echo "you should not see this";
?>
I'm not sure you understand what "exit" states
Terminates execution of the script. Shutdown functions and object destructors will always be executed even if exit is called.
It's normal to do that, it must clear it's memmory of all the variables and functions you called before. Not doing this would mean your memmory would remain stuck and ocuppied in your RAM, and if this would happen several times you would need to reboot and flush your RAM in order to have any left.
or try
trigger_error('Die', E_ERROR);
Related
In a php script I have some test and after the script the html page.
When a test fail i call die("Test 1 failed");
If no test fail the php script reach the end ?> and then load the html code after the php script.
Is this a good procedure? Or I need to write die() or exit() before the end of php script?
No you don't have to write that and this is not best practice. If the script reaches the end without fatal errros it will exit.
If this means "testing" for you, you're wrong. Testing should be done using unit tests. For php there is phpunit. Give it a try, that's the proper way of testing your code.
Edit: As CompuChip says in a comment, the only useful use case for exit is when you're writing a php based shell script that should return an error code. See the parameter section of the documentation for the exit() function.
You should never be using die() or exit in your production PHP scripts except in very specific cases. Instead, re-work your code paths to simply show an error message to the user rather than exiting the script early.
No you don't need that, but when writing console PHP scripts, you might want to check with for example Bash if the script completed everything in the right way. That's when you use exit() or die()
Is the die() or exit() function needed in the end of a php script?
No, PHP will end the script itself. If the script is an included file (called from another file) then it will end script in the included file and then continue with any code in the original file after where you included (if there is any code).
So you put die() or exit() where ever you want or need it.
For testing, put it after each block of code you test. I use them in some parts of testing if I just want PHP to show me something then stop, such as print out an array to make sure it's being constructed correctly etc.
eg:
print_r($array);
exit();
For other code tests, I sometimes just echo "Section A worked", etc, such as within if/else. If I want to know if a particular part of code is working or if some criteria is being met or not (basically, it lets you trace where PHP itself is going within your code).
All that said, don't use die() or exit() in production code. You should use a more friendly and controlled messaging setup. For security reasons and visual, as you could potentially give them some info like "ERROR Failed to load SomethingSecret". Also it doesn't look pretty when you page only half loads and then puts out an on screen error message which likely means nothing to the end user.
Have a read through this:
PHP Error handling: die() Vs trigger_error() Vs throw Exception
No !
This is not recommanded to use it
Use trigger_error or error_log to log the tests in your error.log. Then check it.
No you don't have to use these functions at the end of the script, because it exists anyway at the end of the script.
No need to put a die or an exit at the end of the scipt.
But you may use exit to terminate your script with a specific exit code (by default it's 0).
E.g
$ php -r "/* does nothing */;"
$ echo $?
0
$ php -r "exit(123);"
$ echo $?
123
http://php.net/exit
From the documentation:
The link to the server will be closed as soon as the execution of the
script ends, unless it's closed earlier by explicitly calling
mysql_close().
https://secure.php.net/function.mysql-connect
Nope, you don't need to call die() or exit(0 if you have another code to run, like you HTML code
Am am still on a PHP learning curb. When terminating a script, what is the difference between exit(), die(); and return;?:
within the same file (Single script file)
Within the child of an include
Within the parent of an include
Return returns a value. This can be anything and is meant for functions.
What are the differences in die() and exit() in PHP?
http://php.net/manual/en/function.return.php
die and exit (equivalent functions)
Terminates execution of the script.
return
Returns program control to the calling module. Execution resumes at
the statement following the called module's invocation.
If called from within a function, the return statement immediately
ends execution of the current function, and returns its argument as
the value of the function call. return also ends the execution of an
eval() statement or script file.
If called from the global scope, then execution of the current script
file is ended. If the current script file was included or required,
then control is passed back to the calling file. Furthermore, if the
current script file was included, then the value given to return will
be returned as the value of the include call. If return is called from
within the main script file, then script execution ends. If the
current script file was named by the auto_prepend_file or
auto_append_file configuration options in php.ini, then that script
file's execution is ended.
die vs exit
The difference between die() and exit() in PHP is their origin.
exit() is from exit() in C.
die() is from die in Perl.
PHP Manual
PHP Manual for die:
This language construct is equivalent to exit().
PHP Manual for exit:
Note: This language construct is equivalent to die().
PHP Manual for List of Function Aliases:
die is an alias for master function exit()
DIFFERENT IN OTHER LANGUAGES
die() and exit() are different in other languages but in PHP they are identical.
From Yet another PHP rant:
...As a C and Perl coder, I was ready to answer, "Why, exit() just bails
off the program with a numeric exit status, while die() prints out the
error message to stderr and exits with EXIT_FAILURE status." But then
I remembered we're in messy-syntax-land of PHP.
In PHP, exit() and die() are identical.
The designers obviously thought "Hmm, let's borrow exit() from C. And Perl
folks probably will like it if we take die() as is from Perl too.
Oops! We have two exit functions now! Let's make it so that they both
can take a string or integer as an argument and make them identical!"
The end result is that this didn't really make things any "easier",
just more confusing. C and Perl coders will continue to use exit() to
toss an integer exit value only, and die() to toss an error message
and exit with a failure. Newbies and PHP-as-a-first-language people
will probably wonder "umm, two exit functions, which one should I
use?" The manual doesn't explain why there's exit() and die().
In general, PHP has a lot of weird redundancy like this - it tries to
be friendly to people who come from different language backgrounds,
but while doing so, it creates confusing redundancy.
Return is returns a value (char,int,string,array...) and exit from function.
From php manual :
Note: This language construct is equivalent to die().
But still there are difference between die and exit :
Using die() you can post a string : die("An error occurred");
Same result with using exit()
<?php
echo("An error occurred <br>");
exit(0);
?>
OR if you are cli or unix shell :
Using PHP on the command line, die("An error occurred") simply prints "An error occurred" to STDOUT and terminates the program with a normal exit code of 0.
<?php
fwrite(STDERR, "An error occurred \n");
exit(0); //
?>
While implementing some class I've run into a little problem:
If the script ends and destructors are called because the script has finished, I wanted to trigger an error occasionally.
I thought the trigger_error() function would be of use. However, if error_reporting(-1) the triggered error is not send any longer to STDOUT or STDERR - while it is expected to do so (e.g. if not within the __destructor/termination phase of the script, trigger_error works as expected).
If I echo some message out, it will be send to STDOUT (CLI mode).
I now wonder
how I can trigger an error in this phase of the application?
and/or alternatively how can I detect that currently the script is shutting down because it has successfully ended?
Note: I tested connection_status() but it's useless in my case as it's about connection handling only and merely unrelated. I wonder if there is some function that does the same for the scripts execution status (starting, running, exiting).
Simplified Example Code
This is some very reduced example code to illustrate the issue. Naturally is the error only triggered if it makes sense for the object:
<?php
class TriggerTest
{
public function __destruct()
{
trigger_error('You should have missed something.');
}
}
$obj = new TriggerTest;
exit();
The problem is, that trigger_error() gets executed but the error does not appear anywhere.
How about if you force the error reporting to be a certain setting, trigger the error and then set the error reporting back to it's normal form?
Answer: Just do it. I had some misconfiguration for the error handler and therefore it did not work. My fault.
However it's still interesting if there is any function or similar to determine the execution state on shutdown.
Is there a way to make the code continue (not exit) when you get a fatal error in PHP?
For example I get a timeout fatal error and I want whenever it happens to skip this task and the continue with others.
In this case the script exits.
There is a hack using output buffering that will let you log certain fatal errors, but there's no way to continue a script after a fatal error occurs - that's what makes it fatal!
If your script is timing out you can use set_time_limit() to give it more time to execute.
"Fatal Error", as it's name indicates, is Fatal : it stop the execution of the script / program.
If you are using PHP to generate web pages and get a Fatal error related to max_execution_time which, by defaults, equals 30 seconds, you are certainly doing something that really takes too mych time : users won't probably wait for so long to get the page.
If you are using PHP to do some heavy calculations, not in a webpage (but via CLI, or a cron, or stuff like that), you can set another (greater) value for max_execution_time.
You have two ways of doing that :
First is to modify php.ini, to set this value (it's already in the file ; just edit the property's value). Problem is it'll modify it also for the web server, which is bad (this is a security measure, after all).
Better way is to create a copy of php.ini, called, for instance, phpcli.ini, and modify this file. Then, use it when invoking php :
php -c phpcli.ini myscript.php
This'll work great if you have many properties you need to configure for CLI execution. (Like memory_limit, which often has to be set to a higher value for long-running batches)
The other way is to define a different value for max_execution_time when you invoke php, like this :
php -d max_execution_time=60 myscript.php
This is great if you launch this via the crontab, for instance.
It depends on the exact error type. You can catch errors by creating your own error handler. See the documentation on set_error_handler(), but not all types of errors can be caught. Look at the timeout error you get and see what type it is. If it is one of E_ERROR, E_PARSE, E_CORE_ERROR, E_CORE_WARNING, E_COMPILE_ERROR or E_COMPILE_WARNING then you cannot catch it with an error handler. If it another type then you can. Catch it with the error handler and simply return.
If you have a suitable PHP version (PHP>=5.2 for error_get_last) you can try the technique described here which uses register_shutdown_function and error_get_last.
This won't allow you to "continue" when you get a fatal error, but it at least allows you to log the error (and perhaps send a warning email) before displaying a custom error page to the user.
It works something like this:
function fatalErrorHandler()
{
$lastError = error_get_last();
if (isset($lastError["type"]) && $lastError["type"]==E_ERROR) {
// do something with the fatal error
}
}
...
register_shutdown_function('fatalErrorHandler');
A few points:
you can use ob_clean() to remove any content that was generated prior to the fatal error.
it's a really bad idea to do anything to intensive in the shutdown handler, this technique is about graceful failure rather than recovery.
whatever you do, don't try to log the error to a database ... what if it was a database timeout that caused the fatal error?
for some reason I've had problems getting this technique to work 100% of the time when developing in Windows using WAMP.
The most simple answer I can give you is this function: http://php.net/manual/en/function.pcntl-fork.php
In more detail, what you can do is:
Fork the part of the process you think might or might not cause a fatal error (i.e. the bulk of your code)
The script that forks the process should be a very simple script.
For example this is something that I would do with a job queue that I have:
<?php
// ... load stuff regarding the job queue
while ($job = $queue->getJob()) {
$pid = pcntl_fork();
switch ($pid) {
case -1:
echo "Fork failed";
break;
case 0:
// do your stuff here
echo "Child finished working";
break;
default:
echo "Waiting for child...";
pcntl_wait($status);
// check the status using other pcntl* functions if you want
break;
}
}
Is there a way then to limit the execution time of an function but not all script?
For example
function blabla()
{
return "yes";
}
to make it so that if it is not executed in 25 seconds to return no;
in PHP Does die() gives anything in return when we use it?
In PHP the function die() just quit running the script and prints out the argument (if there's any).
http://php.net/die
Obviously, die() or its equivalent exit() don't return anything to the script itself; to be precise, this code doesn't make much sense:
if (die())) {
echo 'are we dead yet?';
}
However, depending on what you pass as the (optional) argument of die() or exit(), it does return something to the caller, i.e. the command that caused your script to run. Its practical use is usually limited to the cli SAPI though, when you call the script from a command line using php /path/to/script.php.
Observe:
die('goodbye cruel world');
This code would print goodbye cruel world and then return an exit status code of 0, signalling to the caller that the process terminated normally.
Another example:
die(1);
When you pass an integer value instead of a string, nothing is printed and the exit status code will be 1, signalling to the caller that the process didn't terminate normally.
Lastly, die() without any arguments is the same as die(0).
The exit status of a process can be changed to signal different kinds of errors that may have occurred, e.g. 1 means general error, 2 means invalid username, etc.
It is the same as exit() and according to documentation it returns nothing
It does not return. The script is terminated and nothing else is executed.
There's no reason to return something in die/exit. This function terminates php interpreter process inside and returns exit-code to shell. So after calling die() there is no script execution as far as there is no interpreter process which executes the script and that's why there is no way to handle function's return.