Fatal error php

问题:

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.

回答1:

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.

回答2:

"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.

回答3:

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.

回答4:

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.

回答5:

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;

回答6:

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;
    }
}