[PHP] php form with textarea

[adi]

I have a php file with two textarea and one button; i want when i press button, value 
from textarea2 is filled in textarea1.
can u help me?

my try is:

//file1.php
....
if ($action == "change") {
$arie1=$arie2;
}
....
echo "<textarea name='arie1' cols='50' rows='3'>$arie1</textarea>";
echo "<form action=file1.php?&action=change method=post>\n";
echo "<textarea name='arie2' cols='50' rows='3'>$arie2</textarea>";
echo    "<input type='submit' name='submit' value='save'>";
...