add extra field to form not working

Answer 1

You need another } since you added another nested if-else.

However, it'd be far better to refactor using elseif's since those are designed exactly for this type of chaining:

<?php 
if (!$_POST['name']) {echo "Je moet wel je naam invullen a.u.b."; } 
elseif (!$_POST['email']) {echo "Je moet wel je e-mail adres invullen a.u.b."; }
elseif (!$_POST['fename']) {echo "Naam van uw vriend of vriendin invullen."; }
elseif (!$_POST['femail']) {echo "Je moet wel het e-mail adres van uw vriend/familie of kennis invullen. a.u.b."; } 
else {
$name=$_POST['name'];
$email=$_POST['email'];
$fename=$_POST['fename'];
$femail=$_POST['femail'];
$recon=$_POST['recon'];
$recon=htmlspecialchars($recon);
$headers = "From: $email\r\nReply-To: $femail\r\n";


PRINT "Bedankt $name dat u ons heeft aanbevolen.";


mail("$femail", "Computerhulp is nabij!", "

Beste $name , $fename heeft u ons aanbevolen.

$recon
",$headers);

}

?>

Answer 2

When you write a code, keep the block minimum. If you using the IDE, then it will tell you when you missed a }. Use a consistent bracket style and indentation to help you spot a bug.

Here is your code above but will be more readable and easier to find the bug:

<?php

$error = 0;
if (!$_POST['name']) {
  echo "Je moet wel je naam invullen a.u.b.";
  $error = 1;
}
if (!$_POST['email']) {
  echo "Je moet wel je e-mail adres invullen a.u.b.";
  $error = 1;
}
if (!$_POST['fename']) {
  echo "Naam van uw vriend of vriendin invullen.";
  $error = 1;
}
if (!$_POST['femail']) {
  echo "Je moet wel het e-mail adres van uw vriend/familie of kennis invullen. a.u.b.";
  $error = 1;
}
if ( $error == 0 ) {
  $name=$_POST['name'];
  $email=$_POST['email'];
  $fename=$_POST['fename'];
  $femail=$_POST['femail'];
  $recon=$_POST['recon'];
  $recon=htmlspecialchars($recon);
  $headers = "From: $email\r\nReply-To: $femail\r\n";

  PRINT "Bedankt $name dat u ons heeft aanbevolen.";

  mail("$femail", "Computerhulp is nabij!", "

Beste $name , $fename heeft u ons aanbevolen.

$recon
",$headers);

}

See how I use $error to prevent nested if-else.