php exec with WGET creating files

I'm calling exec to run scripts in backgroud using php exec() and wget. But everytime I call this it's creating a file with url parameters in my server. I tried to disable output and tried to store it to a specific file also. Both failed.

here is my code

function execInBackground($cmd)
{
    $cmd = escapeshellcmd($cmd);
    exec($cmd . " > /dev/null &");
}

And I'm calling it like below

execInBackground('wget -q http://example.com/d/do-processing?process=501&res=201');

So now it will create a file named

do-processing?process=501&res=201

in my server. Can you guys please mention is there anything I missed while doing this.

I want to call that url in background without saving any output. In worst case I need to store the output of each call to a specific file instead of creating multiple files.

exec($cmd . " > process.out 2> process.err < /dev/null &");

I tried like above code and didn't worked.