Fill in form in PHP - php

Question

So I've had to make a simple phonebook in PHP, but right now it simply echos the text beneath the form, I however, want it to fill it in the form which says: Phonenumber (When you type in the exact name of someone you it echos their phonenumber)
Here's the Form:
<form action="" method="post">
Naam: <br><input type="text" name="name" /><br>
Telefoonnummer: <br><input type="text" name="phonenumber" disabled />
<input type="submit" value="submit" />
</form>
and here's the PHP (I'm Dutch btw so some of the text is in Dutch):
<?php
if(isset($_POST['name'])) {
$formNaam = $_POST['name'];
$naamPersoon = array ("Ilja Clabbers","Piet Paulusma","Gerrit Zalm");
$telefoonNummer = array ("038-4699776","0568-121212","010-2311512");
if(empty($formNaam)) {
echo 'Vul een veld in.';
} else if ($formNaam == $naamPersoon[0]){
echo "Het telefoonnummer van " . $naamPersoon[0] . " is " .$telefoonNummer[0];
} else if ($formNaam == $naamPersoon[1]){
echo "Het telefoonnummer van " . $naamPersoon[1] . " is " .$telefoonNummer[1];
} else if ($formNaam == $naamPersoon[2]){
echo "Het telefoonnummer van " . $naamPersoon[2] . " is " .$telefoonNummer[2];
} else {
echo "Deze naam staat niet in het archief";
}
}
?>
So basically what I'd like to know is; How do you get the phonenumber belonging to a persons name to be shown in the Form where it says 'Telefoonnummer:'?

Answer 1

A neater solution would be to make a single associative array with key => value pairs:
$naamPersoon = array (
"Ilja Clabbers" => "038-4699776",
"Piet Paulusma" => "0568-121212",
"Gerrit Zalm" => "010-2311512",
);
Then your code would be:
$phonenumber = '';
if (array_key_exists($formNaam, $naamPersoon)) {
echo "Het telefoonnummer van " . $formNaam . " is " . $naamPersoon[$formNaam];
$phonenumber = $naamPersoon[$formNaam];
} else {
echo "Deze naam staat niet in het archief";
}
Alternatively you could keep your two arrays as they are and use array_search to find the index of the name in the first array, then use it as the index you check in the second array
$phonenumber = '';
$index = array_search($formNaam, $naamPersoon);
if ($index === false) {
echo "Deze naam staat niet in het archief";
} else {
echo "Het telefoonnummer van " . $formNaam . " is " . $telefoonNummer[$index];
$phonenumber = $telefoonNummer[$index];
}
Either way you can then use the assigned variable $phonenumber to add the number to the form by echoing it out as the input's value. At which point you can take out the echos if you wish.
<form action="" method="post">
Naam: <br><input type="text" name="name" /><br>
Telefoonnummer: <br><input type="text" name="phonenumber" value="<?=htmlspecialchars($phonenumber)?>" disabled />
<input type="submit" value="submit" />
</form>