Shell Programming and Scripting

<?php 
session_start(); 
// ------------- CONFIGURABLE SECTION ------------------------
$mailto = 'xxx@xxx' ;
$subject = "Inquiry Form" ;
$formurl = "the contact.php form" ;
$errorurl = "the error message .htm" ;
$thankyouurl = "the thank-you message .htm" ;
// -------------------- END OF CONFIGURABLE SECTION ---------------
// load the variables form address bar
$data_start = $_POST['data_start'] ;
$data_end = $_POST['data_end'] ;
// etc.
// remove the backslashes that normally appears when entering " or '
$data_start = stripslashes($data_start);
$data_end = stripslashes($data_end);
// etc.
$http_referrer = getenv( "HTTP_REFERER" );
if (!isset($_POST['email'])) {
 header("Location: $formurl" );
 exit ;
}
// all fields are empty : arrival, departure, pax and comments ==> error
if(empty($data_start) && empty($data_end) && empty($pax)&& empty($comment)){ 
exit("You have not specified any booking details"); 
exit;
} 
$arrive = explode($_POST['$data_start'],"/");
$arrive[0] =yyyy
$arrive[1] =mm
$arrive[2] =dd
// swap round
$data_start = sprintf("%s/%s/%s",$arrive[2],$arrive[1],$arrive[0]);
}
if ( ereg( "[\r\n]", $name ) || ereg( "[\r\n]", $email ) ) {
 header("Location: $errorurl" );
 exit ;
}
if (!isset($_POST['email'])) {
 header("Location: $formurl" );
 exit ;
}
$messageproper =
 "This message was sent from:\n" .
 "$http_referrer\n\n" .
 "------------------------- COMMENTS -------------------------\n\n" .
 "Date of Arrival:  " .  
 "$data_start\n" . 
 "Date of Departure:  " . 
 "$data_end\n" .  
 "\n\n---------------- END OF MESSAGE -----------------\n" ;
mail($mailto, $subject, $messageproper, "From: \"$name\" <$email>\r\nReply-To: \"$name\" <$email>\r\nX-Mailer: chfeedback.php 2.04" );
header( "Location: $thankyouurl" );
 // delete the cookie so it cannot sent again by refreshing this page
 setcookie('tntcon','');  
 exit;
 
 // if verification code was incorrect then return to contact page and show error
 header("location:contact.php?Title=$Title&name=$name&email=$email&phone=$phone&fax=$fax&nationality=$nationality&data_start=$data_start&data_end=$data_end&result=$result&pax=$pax&children=$children&payment=$payment&appick=$appick&purpose=$purpose&comment=$comment&wrong_code=true");
exit;
} else {
 echo "You entered a wrong verification code. Please go back and try again.";
 exit ;
}
?>

...
} 
$arrive = explode($_POST['$data_start'],"/");
$arrive[2] =yyyy
$arrive[1] =mm
$arrive[0] =dd
// swap round
$data_start = sprintf("%s/%s/%s",$arrive[2],$arrive[1],$arrive[0]);
}
...

...
} 
$arrive = explode($_POST['$data_start'],"/");
$arrive[0] =dd
$arrive[1] =mm
$arrive[2] =yyyy
// swap round
$data_start = sprintf("%s/%s/%s",$arrive[2],$arrive[1],$arrive[0]);
}
...