removing from file

[Pouncer]

The code below adds text to the file in the format of:

www.my-site.com/filename.php?data=hello

<?php
$filename = 'test.txt';
$somecontent = $_GET['data'] . "\n"; 

if (is_writable($filename)) {

   if (!$handle = fopen($filename, 'a')) {
         echo "Cannot open file ($filename)";
         exit;
   }

   if (fwrite($handle, $somecontent) === FALSE) {
       echo "Cannot write to file ($filename)";
       exit;
   }
   
   echo "Success, wrote ($somecontent) to file ($filename)";
   
   fclose($handle);

} else {
   echo "The file $filename is not writable";
}
?>

but then how can i make a php file which will allow me to remove the word 'hello' from test.txt

www.my-site.com/remove.php?data=hello
any help on this please?