Struggling with required field with PHP form -

this first time using php , haven't clue i'm doing. i've taken template , coded html form go it, works except there's no required fields can send blank email if click submit. i'd have error message come when 'name' , 'email' , 'message' inputs empty. can help?

<?php  $emailfrom = "joejlomax@gmail.com"; $emailto = "joejlomax@gmail.com"; $subject = "t/v/c inquiry"; $name = trim(stripslashes($_post['name']));  $tel = trim(stripslashes($_post['tel']));  $email = trim(stripslashes($_post['email']));  $message = trim(stripslashes($_post['message']));    // validation $validationok=true; if (!$validationok) {   print "<meta http-equiv=\"refresh\" content=\"0;url=error.php\">";   exit; }  // prepare email body text $body = ""; $body .= "name: "; $body .= $name; $body .= "\n"; $body .= "email: "; $body .= $email; $body .= "\n"; $body .= "message: "; $body .= $message; $body .= "\n";  // send email  $success = mail($emailto, $subject, $body, "from: <$emailfrom>");  // redirect success page  if ($success){   print "<meta http-equiv=\"refresh\" content=\"0;url=contactthanks.php\">"; } else{   print "<meta http-equiv=\"refresh\" content=\"0;url=error.php\">"; } ?> 

you can use empty check if variable is.. empty.

$validationok = true; if(empty($name) or empty($tel) or empty($email) or empty($message)) {     $validationok = false; } if (!$validationok) {     print "<meta http-equiv=\"refresh\" content=\"0;url=error.php\">";     exit; }