Description:
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Today I had the issue that the use of a function was silenty ignored.

On the system the configuration directive 

disable_functions exec

was set.

In a script exec was used.

Even I wrote something like:

ini_set('display_errors', 'On');
error_reporting(E_ALL);
$lastLine = exec($command, $output, $returnValue);

during debugging no INFO/WARN/ERROR was shown that the exec was blocked by configuration.

I would expect a WARN like "Use of function exec is blocked by configuration on line xxx" or something like this