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POPreventing PHP fatal error traceback output when using custom shutdown handler
 

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  1. POPreventing PHP fatal error traceback output when using custom shutdown handler
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    <p>I must be missing something in my understanding of handling PHP errors, specifically suppressing their output. When a fatal error occurs, I expect my shutdown handler function to process it gracefully and terminate script execution. This works as expected. <strong>However, I can't seem to prevent PHP from outputting the information about the fatal error.</strong></p> <p>My php.ini file contains the following directives:</p> <pre><code>error_reporting = E_ALL | E_STRICT display_errors = Off </code></pre> <p>I set <code>error_reporting</code> to report everything and I use a custom error handler to throw exceptions. My expectation is that <code>display_errors = Off</code> will prevent ANY error messages from being displayed.</p> <p>Anyway, when a fatal error occurs the custom error handler is bypassed (because script execution stops immediately) and the shutdown handler executes.</p> <p>Now, on to my simplified code:</p> <pre><code>error_reporting(E_ALL | E_STRICT); ini_set('display_errors', 'Off'); function shutdown_handler() { $err = error_get_last(); $fatal = array(E_ERROR, E_PARSE, E_CORE_ERROR, E_COMPILE_ERROR); if ($err &amp;&amp; in_array($err['type'], $fatal)) { echo "\n\ntest fatal error output\n\n"; } exit(); } register_shutdown_function('shutdown_handler'); </code></pre> <p>To test it I generate an "Allowed memory size exhausted" fatal error like so:</p> <pre><code>// max out available memory $data = ''; while(true) { $data .= str_repeat('#', PHP_INT_MAX); } </code></pre> <p>Because i have <code>display_errors = Off</code> I expect this to only produce the following output (as per the shutdown handler):</p> <pre><code>test fatal error output </code></pre> <p>But instead I continue to receive:</p> <pre><code>PHP Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 2147483648 bytes) in /home/daniel/mydev/php/test0.php on line 24 PHP Stack trace: PHP 1. {main}() /home/daniel/mydev/php/test0.php:0 PHP 2. str_repeat() /home/daniel/mydev/php/test0.php:24 test fatal error output </code></pre> <p><strong>What am I missing that will prevent this error trace from outputting?</strong></p> <hr> <p><strong>CONCLUSION</strong></p> <p>It appears, as @Cthos sagely noted, that "E_ERROR and display_errors don't play nicely together."</p> <p>This is also the case for E_PARSE (and I assume E_CORE_ERROR/E_COMPILE_ERROR, but I didn't break my PHP installation to test it). I suppose it makes sense that PHP would force the error traceback into STDOUT in these cases because if it didn't you might never know if/why things were going wrong.</p> <p>So a solution in this case would be:</p> <ol> <li>As @Cthos suggested, silence E_ERROR notifications in php.ini: <code>error_reporting = (E_ALL &amp; ~ E_ERROR)</code> or at runtime using <code>error_reporting(E_ALL &amp; ~ E_ERROR);</code></li> <li>Update the shutdown handler to check if the last error was of type E_ERROR and perform the appropriate actions if so.</li> </ol> <p>As for the other fatals like E_PARSE, E_CORE_ERROR, etc. you just have to make sure your code is correct and that your PHP works. If you try to silence E_PARSE errors and handle them in your shutdown function it won't work because parse errors prevent PHP from ever getting that far.</p> <p>So, an updated/working shutdown handler looks like this:</p> <pre><code>error_reporting(E_ALL &amp; ~ E_ERROR); function shutdown_handler() { $err = error_get_last(); if ($err &amp;&amp; $err['type'] == E_ERROR) { $msg = 'PHP Fatal Error: '.$err['message'].' in '.$err['file']. ' on line '.$err['line']; echo $msg, PHP_EOL; } exit(); } </code></pre>
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    1. COMayhap you should have a custom error handler instead? http://www.php.net/manual/en/function.set-error-handler.php
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    2. CO@Cthos -- as the question states, I already use a custom error handler. When a fatal error occurs script execution stops immediately and a custom error handler doesn't get called. A custom shutdown handler, however, can still run.
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    3. COHrm, I failed at reading comprehension then, however I had thought Fatals would still go to said handler. Experimentation time.
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