Php – Form validate with foreach only runs first loop

As brombeer mentioned in a comment to your original post, you are redirecting away from the page after the first database update.

You need to do the redirect after all of the loops have run.

Below is your original code, but I have moved the redirect to take place after the foreach loop completes its iterations.

if ($_SERVER["REQUEST_METHOD"] == "POST" and $_POST["type"] == "bulk-update") {
    $ids = explode(',', $_GET['ids']);
    foreach ($ids as $id) {
        $post_data = [
            'team' => $_POST['team_' . $id],
            'player1' => $_POST['player1_' . $id],
            'email' => $_POST['email_' . $id],
        ];

        if (empty($post_data["team"])) {
            $teamErr = "Fyll i namnet på laget";
        } else {
            $team = test_input($post_data["team"]);
        }

        if (empty($post_data["player1"])) {
            $player_1Err = "Fyll i namn på spelare 1";
        } else {
            $player_1 = test_input($post_data["player1"]);
            // check if name only contains letters and whitespace
            if (!preg_match("/^[a-zåäöÅÄÖ -]+$/i", $player_1)) {
                $player_1Err = "Bara bokstäver och mellanslag är giltiga";
            }
        }

        if (empty($post_data["email"])) {
            $emailErr = "Fyll i en e-postadress";
        } else {
            $email = test_input($post_data["email"]);
            $email = strtolower($email);
            // check if e-mail address is well-formed
            if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
                $emailErr = "Detta är inte en giltig e-postadress";
            }
        }

        if ($teamErr == '' && $player_1Err == "" && $emailErr == "") {
            // Update the teams in the database
            $stmt = $db->prepare('UPDATE anmalningar SET team = ?, player1 = ?, email = ? WHERE id = ?');
            $stmt->execute([$team, $player_1, $email, $id]);
        }
    }
    // Redirect and output message, after the loop has run
    header("Location: /tavlingar/skapa_csv.php?bulk-upd&ids={$_GET['ids']}");
    exit();
}

function test_input($data)
{
    $data = trim($data);
    $data = stripslashes($data);
    $data = htmlspecialchars($data);
    $data = ucwords($data);
    return $data;
}