my if statement is returning command not found

Question

in my script an if statement returns:

line 3: []: command not found

the statement:

if ["$(pidof -x $(basename $0) -o %PPID)"]; then
    echo process already running; exit;
fi

what I tried:

if [["$(pidof -x $(basename $0) -o %PPID)"]]; then
    echo process already running; exit;
fi

if [["$(pidof -x basename $0 -o %PPID)"]]; then
    echo process already running; exit;
fi

if ["$(pidof -x basename $0 -o %PPID)"]; then
    echo process already running; exit;
fi

if [[$(pidof -x basename $0 -o %PPID)]]; then
    echo process already running; exit;
fi

none seems to work.I get similar error.

line 3: [[]]: command not found

I got the code from here: https://linuxpip.org/rclone-examples/ https://forum.rclone.org/t/continuous-syncing/12377/2

I did research here: https://wiki.bash-hackers.org/syntax/ccmd/conditional_expression and looked at the man bash’s Compound Commands section but they don’t seem to help.

please help Thank you!