#php
<?php
if(isset($_POST['click'])){
$file = "клики.txt";
$clicks = @file($file);
$current_clicks = $clicks[0];
++$current_clicks;
$fh = fopen("$file", "w");
@fwrite($fh, $current_clicks);
fclose($fh);
} 
?> 

<form action="test.php" method="post">
<input type="HIDDEN" name="click" />
<input type="submit" />
</form> 

<?php
$file = "клики.txt";
$clicks = @file($file);
$current_clicks = $clicks[0];
echo "Эту кнопку уже нажало $current_clicks людей";
?>