Sample code to show how to handle database error messages in PHP according to the current user's status - See https://blog.skyplabs.net/2011/03/19/afficher-les-erreurs-sql-de-php-seulement-aux-personnes-concernees/ (French)

db.php

<?php
// Connection variables.
$db_type = "";
$db_host = "";
$db_user = "";
$db_password = "";
$db_database = "";

// We test the connection with the database.
try
{
    $db = new PDO($db_type.":host=".$db_host.";dbname=".$db_database, $db_user, $db_password);
}
catch (Exception $e)
{
    // If the current user has the administrator status, we display the
    // complete error message.
    if (isset($_SESSION['status']) && $_SESSION['status'] == 'admin')
        die("Error : " . $e->getMessage());
    // Else, we display a generic error message with no details.
    else
        die("Error : Impossible to establish the connection with the database.");
}

// Used to handle database error messages.
function mySqlError($db)
{
    // If the current user has the administrator status, we display the
    // complete error message.
    if (isset($_SESSION['status']) && $_SESSION['status'] == 'admin')
        print_r($db->errorInfo());
    // Else, we display a generic error message with no details.
    else
        echo "Error : Sorry, an SQL error has occured.";
}
?>

example.php

<?php
$exemple_of_query = $db->prepare("INSERT INTO table VALUES (:var1, :var2, :var3)");
$exemple_of_query->execute(array('var1' => $var1, 'var2' => $var2, 'var3' => $var3))
or die(mySqlError($db));
?>