<?php
if($_POST)
{
$message = $_POST["veri"];
$file = "yazi.txt";
if (($fd = fopen($file, "a")) !== false) { 
  fwrite($fd, $message . "\n");   
  fclose($fd); 
}
}
?>
<form method="POST" action="">
<textarea name="veri" type="text" value=""></textarea><br>
<input type="submit" value="ekle">
</form>