Another method is to see if you've surpassed the error checking in your code by accident. Search all your code for any instance of error_reporting(). If you call it without parameters, it just returns the current level, and is harmless. If you call it with a parameter, such as 0 (zero), it will turn off error reporting.
You can test for this in CodeIgnitor by looking at their core library under ../system/core/Common.php and finding a section that's at about line 615 that looks like:
if (($severity & error_reporting()) !== $severity)
{
return;
}
Add something like:
if (($severity & error_reporting()) !== $severity)
{
echo "Suppressing errors!";
return;
}
and you should be able to trap for surpassed errors, and debug from there.