Working with something that needs a shell access, like working with awesome imagick function and stuck with sh: convert: command not found
The thing is it works when the same command that run from php script is run on the command line.
It is a path issue.
exec("convert soruce.ext converted.ext", $report);
Here the report would tell how it goes and it will get back with the news
sh: convert: command not found
To get the full path of the command and use it
exec("full-path-to-convert source.ext converted.ext", report);
The above would work for any command that creates related problems.