PHP shell_exec() Command not found

Question

I need to execute a program using php, the file in question is ClustalW (clustalw2). My apache user is http using fish shell, so I moved clustalw2 to /srv/http/Clustal and added the dir to fish path.
If I log in into http using terminal and run clustalw2 -INFILE=input_file -OUTFILE=output_file everything works as expected.
But every time I run shell_exec('clustalw2 -INFILE=input_file -OUTFILE=output_file'); nothing happens and I get this error log: sh: line 1: clustalw2: command not found

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If I run:

<?php
echo "USER: ".shell_exec('whoami')."<br>";
echo "SHELL: ".shell_exec('echo "$SHELL"')."<br>";
echo "WHICH clustalw2: ".shell_exec('which clustalw2');

Output:
USER: http
SHELL: /usr/bin/fish
WHICH clustalw2:

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If I run which clustalw2 in terminal using http user:

/srv/http/Clustalw/clustalw2

Answer 1

Your program can't find clustalw2 because clustalw2 isn't in the $PATH.

In your case, the easiest solution is to replace clustalw2 with the full path, /srv/http/Clustalw/clustalw2 as the first parameter to shell_exec.