increment a number, but needs persistence

[sdowney717]

how can this be done?
so that the number will increment +1 every time a button is pushed?
I push the button, but cant get the number to go up

<?php
$inc=0;

if (!empty($_POST['button'])){
switch ($_POST['button']){
case 'button1':
$yes = 'yes 1';
echo 'time '.time().'<BR>';

echo 'increment number '.$inc.'<BR>';
$f = sum();
echo $f.'<BR>';
echo 'increment number '.$f.'<BR>';

$inc = sum();
echo 'increment number '.$inc.'<BR>';
echo "pushed button 1".'<BR>';

//echo $inc;
//echo $inc;
$q= "select titles, author from bookdata where id = '$f'";
echo "$q".'<BR>';

break;
case 'button2':
echo "pushed button 2".'<BR>';
break;
case 'button3':
echo "pushed button 3".'<BR>';
break;


default:
echo "????/".'<BR>';
break;
}
}
else
{
//$inc = 0;
}

?>


<form action="increment.php" method="post">
<div>
<input type="submit" name="submit" value="submit"/>
<button type="submit" name="button" value="button1">Button 1</button>
<button type="submit" name="button" value="button2">Button 2</button>
<button type="submit" name="button" value="button3">Button 3</button>
</div>
</form>

<?php

function sum()
{
global $inc;
$inc = $inc + 1;
}

function sub()
{
global $inc;
$inc = $inc - 1;
}

[shadylookin]

Once a php script has finished executing all the variables are gone.
A work around is to use hidden inputs to keep values. like

<input type='hidden' name="numOfTimesClicked" value="2"/>

then look for that in the php file