Try-catch suppress? « phpslacker

Try-catch suppress?

PHP never ceases to amaze me. Just the other day a colleague discovered that you can suppress error messages reported by file_get_contents() using the try-catch statement. That should’ve raised an eyebrow. In case you missed it here’s the sample code run from php’s interactive console:

Sample code, nothing odd (yet)

qbook:mobilesns quinton$ php -a Interactive mode enabled


<?php
echo file_get_contents('bleh');
Warning: file_get_contents(bleh): failed to open stream: No such file or directory in /Library/WebServer/workspaces/default/mobilesns/- on line 3
Call Stack:

   19.3675     673612   1. {main}() /Library/WebServer/workspaces/default/mobilesns/-:0

   19.3914     673676   2. file_get_contents('bleh') /Library/WebServer/workspaces/default/mobilesns/-:3
Dump $_SERVER

Dump $_GET

Dump $_POST

Predictably, the code snippet above confirms that php will report an error if you attempt to open a file that does not exist. You may have noticed, my php installation has some extra debug output because I’m using the XDebug extension. I recommend it. Highly.

This is where it gets weird

Again, from the console. Here we place the same call to read a non-existent file within a try-catch statement.

qbook:mobilesns quinton$ php -a Interactive mode enabled


<?php
try

{
echo file_get_contents('bleh');
}

catch (Exception $e)

{
echo "Exception is caught";              
}

This time around the error is not reported by php nor is the “catch” executed proving that the error message is suppressed. Is it a bug or a side-effect? Anyone have any thoughts on this? “Its not a bug its a feature!” ~ comes to mind

My php version, in case you’re wondering

qbook:mobilesns quinton$ php -v PHP 5.2.5 (cli) (built: May 27 2008 11:45:48) Copyright (c) 1997-2007 The PHP Group Zend Engine v2.2.0, Copyright (c) 1998-2007 Zend Technologies with Xdebug v2.0.4, Copyright (c) 2002-2008, by Derick Rethans with Zend Debugger v5.2.14, Copyright (c) 1999-2008, by Zend Technologies

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on March 19, 2009 at 10:17 pm Comments (15)
Tags: bugs, php

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15 Comments Leave a comment

On March 20, 2009 at 4:46 pm Dever said:

On failure, file_get_contents() will return FALSE.

Reply
- On March 20, 2009 at 4:50 pm phpslacker said:
  
  Erm yes I know that. Look closer at the blog post. With error_reporting=E_ALL and display_errors=1 file_get_contents() is supposed to blurt out a php error BUT when done within a try-catch the error is mysteriously suppressed
  
  Reply
On March 20, 2009 at 4:54 pm Frenck said:

Most of PHP does not work with Exceptions yet. file_get_contents returns a FALSE on failure, like Dever already wrote.

file_get_contents throw a PHP Error in your example, not exception. Therefor, you can’t catch it with a try/catch block.

Why it surpresses the orginal PHP error… I can’t answer, seems like a bug to me!

../Frenck

Reply
- On March 20, 2009 at 5:04 pm phpslacker said:
  
  @Dever @Frenck thanks for posting but you both state the obvious
  
  The question is: Why is the php error suppressed from within the try-catch?
  
  Reply
On March 20, 2009 at 5:04 pm John J. said:

This appears to be a oddity of the interactive console. If you run the same code from a file at the command line it does display the warning. (tested with PHP 5.2.5):
test.php:

~$ php ./test.php

Warning: file_get_contents(blah) [function.file-get-contents]: failed to open stream: No such file or directory in /home/jaj/public_html/test.php on line 3
Call Stack
# Time Memory Function Location
1 0.0003 48388 {main}( ) ../test.php:0
2 0.0003 48388 file_get_contents ( ) ../test.php:3

Reply
- On March 20, 2009 at 5:08 pm phpslacker said:
  
  @John Well I wouldn’t blame the interactive console just yet. I originally encountered that “bug” by running a cli script just as u did
  
  It was just for the purpose of the blog post that i presented the issue from the interactive console
  
  Reply
On March 20, 2009 at 5:31 pm Dever said:

Take a look at this in order to change the error into an exception.
The first comment has a nice code sample:
set_error_handler(create_function(‘$a, $b, $c, $d’, ‘throw new ErrorException($b, 0, $a, $c, $d);’), E_ALL);

Reply
On March 20, 2009 at 5:39 pm zeek said:

I get a warning with try catch, also on cli
php 5.2.6

Reply
On March 20, 2009 at 5:40 pm Sascha said:

Warning: file_get_contents(bleh): failed to open stream: No such file or directory in….

qorks perfectly fine for me with 5.2.6-3ubuntu2 when I copy your example into a file and execute it with php test.php.

Reply
- On March 20, 2009 at 5:55 pm phpslacker said:
  
  @zeek @Sascha i think it may be a bug introduced by one of the extensions i have installed. I’m using xDebug, Zend Debugger, APC and who knows what else
  
  Reply
On March 20, 2009 at 6:07 pm zeek said:

Xdebug, Apc, tidy, mcrypt + standard extensions are running and working nicely together.

But your combination of Xdebug and Zend Debugger is a perhaps the problem…

Reply
On March 20, 2009 at 7:03 pm Robert said:

test generates an error as expected on my local machine running 5.2.5

my guess would also be that one of your debuggers is the culprit

Reply
On March 21, 2009 at 6:51 am Quinton Parker’s Blog: Try-catch suppress? : Dragonfly Networks said:

[...] this new entry to his blog Quinton Parker looks at some strangeness he’s found around the try/catch [...]

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On March 22, 2009 at 4:33 pm Giorgio Sironi said:

Get the warning with php 5.2.6-2ubuntu4.1.

Reply
On March 23, 2009 at 4:47 am Quinton Parker’s Blog: Try-catch suppress? | Cole Design Studios said:

[...] this new entry to his blog Quinton Parker looks at some strangeness he’s found around the try/catch [...]

Reply

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