PHP server stops my loop. Why?

Question

I'm trying to verify the 3x + 1 problem, by running a PHP script online and evaluating all numbers.

I have an infinite loop running, but the server stops my loop when the value reaches about 35,000.

I'm guessing the termination is caused when my HTTP connection resets and the server is no longer serving my request.

I want to have it run as long as it can, eating up the server's resources if it wants to. How do I do it? Cronjobs?

Here's the script, the "End" is never printed.

class Collatz_Verify
{
    public function Collatz_Verify()
    {
        // open output file
        $file = 'verified_nums.txt';
        $outFile = fopen($this->NUMBERS_FILENAME, 'a');
    }

    public function verify()
    {
        $num = 0;
        while(1)
        {
            $num += 1;
            # call collatz!!
            if($this->collatz($num) == 1)
                   fwrite($this->outFile, $num);
        }
        print "ah, crap! End!";
    }

    public function collatz($num)
    {
        if ($num == 1)
            return 1;
        if (($num % 2) == 0)
            return $this->collatz($num/2);
        else
            return $this->collatz((3*$num) + 1);
    }
}


// Fire away!
$ver = new Collatz_Verify();
$ver->verify();

?>

Does the server give an error message when the script stops? — Jon
– Jon, Commented Feb 7, 2013 at 15:22
don't run it under a webserver, then. command line php doesn't have resource limits enabled by default. — Marc B
– Marc B, Commented Feb 7, 2013 at 15:23
Run it from the command line. Timeouts are imposed (normally) on requests served by a webserver. — lll
– lll, Commented Feb 7, 2013 at 15:23
Are you reaching the max execution time? php.net/manual/en/function.set-time-limit.php — user20232359723568423357842364
– user20232359723568423357842364, Commented Feb 7, 2013 at 15:23

Ed Meacham · Accepted Answer · 2013-02-07 15:24:46Z

2

You could run it from command line... you'll eventually stop due to lack of resources though.

Running from command line will prevent you from having to do the ini_set mentioned just before my post. (see: http://www.php.net/manual/en/info.configuration.php#ini.max-execution-time)

answered Feb 7, 2013 at 15:24

Ed Meacham

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5 Comments

Ed Meacham Over a year ago

mpaepper's right about the while(1) logic -- but to use php via CLI: php.net/manual/en/features.commandline.php - php.net/manual/en/features.commandline.usage.php

Ed Meacham Over a year ago

the easiest way is via ssh, or if you have direct access to the machine or vm, open a terminal

nimbudew Over a year ago

But why does a script executed from CLI ignore the max_exeution_limit in the php.ini?

Ed Meacham Over a year ago

See the documentation: php.net/manual/en/features.commandline.differences.php max_execution_time 0 (unlimited) PHP in a shell environment tends to be used for a much more diverse range of purposes than typical Web-based scripts, and as these can be very long-running, the maximum execution time is set to unlimited.

Ed Meacham Over a year ago

let us continue this discussion in chat

Community · Accepted Answer · 2023-11-17 19:32:19Z

2

The end never prints, because you are in a while(1) loop and thus the statement afterwards will never be reached. Your script is probably terminated because of your settings in php.ini for the variable max_execution_time

Edit: Try to use the function set_time_limit() https://www.php.net/manual/en/function.set-time-limit.php to be able to increase the time in your script.

edited Nov 17, 2023 at 19:32

CommunityBot

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answered Feb 7, 2013 at 15:25

mpaepper

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1 Comment

nimbudew Over a year ago

oh! interesting. But my web server disabled it. Warning: set_time_limit() has been disabled for security reasons. I'll edit the php.ini

Tim Holum · Accepted Answer · 2013-02-07 15:23:41Z

1

php has a max_execution_time limit, If you want it to run for longer, you could try ini_set('max_execution_time' ,100 ); //Replace 100 with how many seconds you want it to be able to run

answered Feb 7, 2013 at 15:23

Tim Holum

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2 Comments

Tim Holum Over a year ago

you also in your php.ini file ( usually /etc/php.ini ) look for max_execution_time and edit it there as well

nimbudew Over a year ago

yeah, it's set to 30 currently.

Arjan · Accepted Answer · 2013-02-07 15:48:31Z

1

There are two possible reasons for PHP to stop executing your loop.

The first is that the execution time limit is reached. The second is that the maximum nesting level is reached (due to recursion in collatz()).

The maximum nesting level is 100 (I'm not aware of ways to change that). The default execution time limit is 30 seconds. You can increase that, as the other answers show.

To find out what the reason is that your script stops, you should set display errors to on and/or check the error log of the web server. Also you could check the output file and start with the last successful number. So if the last number in the output file is 34998 then change the line $num = 0; into $num = 34998;.

answered Feb 7, 2013 at 15:48

Arjan

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Comments

Ed Heal · Accepted Answer · 2013-02-07 15:25:39Z

0

In the PHP.ini file there are limits on time for the script to execute/memory that the script can use.

See http://php.net/manual/en/info.configuration.php for full details

answered Feb 7, 2013 at 15:25

Ed Heal

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