<form action="" method="POST">
<input type="text" name="link">
<input type="submit" name="button" value="Изпрати">
</form>
<?php
if($_POST[button]){
$link=$_POST['link'];
if(!ereg("http://") || !ereg("www.")) {
echo "Въведете линк!"; }
else {
$query=mysql_query("INSERT INTO table VALUES ('$link')") or die(mysql_error());
echo "Готово";
}
?>