Description:
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When attempting to call the zip command from php, it silently fails. Other commands to create and delete files etc work fine. Using correct path to zip etc. No errors, just fails. Running same command from terminal works.

Test script:
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$zip=`which zip`;
$res=shell_exec("$zip test.zip test.txt");


Expected result:
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zip file should be created

Actual result:
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Nothing. No errors, although the response variable $res contains what appears to be part of the zip file data. Seems like the output from zip is not going to the file, but being sent to the virtual terminal.