Revision 3defb946-9fd3-4d38-8823-9b7823b666ef

I want to use php or jquery to control gpio pins on my raspberry pi 2.
I have apache installed.
When i execute python files using LXTerminal, they work fine.
I have made the .py files executable and added www-data to sudoers file.

This is the php code:

    <html>
    <head>
    <?php 
    if (isset($_POST['ON']))
    {
    exec('sudo python var/www/gpio/on.py');
    }
    if (isset($_POST['OFF']))
    {
    exec('sudo python var/www/gpio/off.py');
    }
    ?>
    </head>
    <body>
    <form method="post">
    <button name="ON">LED On</button>
    <button name="OFF">LED Off</button>
    </form>
    </body>
    </html>

python script
    
    #!/usr/bin/python
    import RPi.GPIO as GPIO
    GPIO.setwarnings(False)
    GPIO.setmode(GPIO.BOARD)
    GPIO.setup(40, GPIO.OUT)
    GPIO.output(40, 1)

What's the mistake?
Thanks in advance :)