Output a Single Row from a MySQL Database in a Simple PHP Site without CSS

Question

I have a small database for a school project that is built like:
Seatnumber | Name | Age | Address

and has around 30 Lines...

I want a blank site with an input field where I can enter one of the 4 values and get as an output the whole row where one value is correct.

So I mean when I had the table like this:

Seatnumber	Name	Age	Address
1	Smith	24	Berlin
2	Mueller	25	Berlin
3	Peter	24	Bonn

I want to enter in the field the number 24 (Probably I need a dropdown field in front of the input field in which category I want to search the value?) and want to output the complete row 1 & 3 because both had the age "24"

Currently I got this that can output the whole table

$sql = "SELECT * FROM Sitzplan";
foreach ($pdo->query($sql) as $row) {
   echo "Sitzplatz: ".$row['Sitznummer'].". ".$row['Name']." ".$row['Alter']."<br />";
   echo "Wohnort: ".$row['Wohnort']."<br /><br />";
}

I Hope you guys can help me with this because I only know Lua and want to have it on a website because of our stupid school rules for not using external programs.

And already many Thanks for the Help! I hope my English is not so bad that nobody can read it. And the last thing I created the table simply with PHPmyAdmin if this is important

Answer 1

Use a form and get their values using $_POST

<form method="post">
  <select name="field">
    <option value="age">Age</option>
    <option value="name">Name</option>
  </select>
  <input type="text" name="value" placeholder="Value..." />
  <button>Submit</button>
</form>

On user input, make request a little different :

if ($_POST) {
  $field = $_POST['field'];
  $value = $_POST['value'];
  $req = "SELECT * FROM Sitzplan WHERE $field = ?";
} else {
  $req = "SELECT * FROM Sitzplan";
}

$sth = $pdo->prepare($req);
$sth->execute([$value ?? null]); // prevents error if $value is undefined (on no user input)
$results = $sth->fetchAll();

Note that I am preparing the request before executing it
Then simply loop $results like you did

foreach ($results as $row) {
   echo "Sitzplatz: ".$row['Sitznummer'].". ".$row['Name']." ".$row['Alter']."<br />";
   echo "Wohnort: ".$row['Wohnort']."<br /><br />";
}