重现PHP未定义索引错误

Question

[Mon Nov 11 11:07:18 2013] [error] [client nnn.nnn.nnn.nnn] PHP Notice:  Undefined index: population in /home/client/locale-qa/include/header.php on line 11

I'm attempted to reproduce this log error from a 300+MB Apache log file my vendor sent. The vendor cannot provide the code found in header.php (frustrating), but this error, and many like it seems to be at the root of an HTTP response we are getting on our side.

I'm not a PHP-ninja, but I understand the error enough to see it suggests that some associative index label may not be defined.

Anything simple that would allow me to reproduce the error in a sandbox Apache build I have would be helpful.

Answer 1

<?php
echo $_REQUEST["population"]; //Undefined index: population 

//Solution  

$population = isset( $_REQUEST["population"] ) ? $_REQUEST["population"] : null; //if not set then set it to null
?>

Answer 2

Line 11 of header.php references $somearray['population'] , but there is no 'population' key in that array.

You will need to look at header.php to see how it's populating $somearray , and why it might not be providing a value for 'population'.

It's often a good idea to use isset($somearray['population']) or array_key_exists('population', $somearray) to avoid an "undefined index" error, but you'll have to decide what the script should do if the key does not exist in the array.

Answer 3

Try grep -ing for the timestamp and the ip in the log file, that should narrow it down enough so you can try them all and see if the error surfaces (hoping that this was a GET request). A 300M+ file should not be a problem for that. The for the usual apache log format this would look something like this:

grep -iE "x\.x\.x\.x.*\[11/\Nov\/2013:11:07:19" the_log_file.log

(the x-es where the ip address goes). You should see something like this at the end of the lines:

.... GET /some_path/some.php?foo=bar HTTP/1.1" 200 42

From this, you can grab the path, append it you your server's domain and see if the error is there or not. You can ignore the image, css and other static asset GETs, but if you have some rewrite rules or other way of PHP being executed on those lines too then check those as well.

If you are on a unix like system you probably have grep already, if you are not you can grab a copy for windows here: http://gnuwin32.sourceforge.net/packages/grep.htm