[AndrewD]

Originally Posted by Dean C

I believe you also have to enable the module in php.ini

I recently enabled the gd module and had to uncomment a line

No, I don't think that's the point.

The question is how to write code that is safe to this setting? (Indeed, why should one have to bother?)

In the meantime, this is what I've tried, seemingly successfully, but I've no idea if this is adequate, failsafe, etc.

PHP Code:

// Guard against uncontrolled use of zlib library
$zlib = ini_get('zlib.output_compression');
ini_set('zlib.output_compression', 'Off');

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// Restore setting of zlib library
ini_set('zlib.output_compression', $zlib);