<body>
<form action="vista.php" method="post" target="_self">
INGRESE CODIGO:
<input name="CODIGO" type="text" />
<input name="Ingreso" type="submit" value="INGRESAR" />
</form>
<?php
//echo "VALOR:".$_POST["CODIGO"];
switch ($_POST['CODIGO']){
case cs1: echo("<p align='center'><img src='<? Echo($_POST['codigo'] . 'jpg') ?>' width='847' height='567' /></p>");
break;
}
?>
</body>
</html>