database connection. Misunderstanding of error messages - php

Question

I am receiving these error messages:
Warning: PDO::__construct() expects parameter 4 to be array, string given in C:\wamp\www\MyProjects\GhislainPOO\personnages.php on line 2. There is no password required, I am wondering what it's meant by array here?
Fatal error: Call to a member function query() on a non-object in C:\wamp\www\MyProjects\GhislainPOO\personnages.php on line 3. is $bdd not an object, although I use "new PDO"?
PHP
<?php
$bdd= new PDO ('localhost', 'POO', 'root', '');
$bdd->query( "SELECT * FROM jeux_combats");
$result = $bdd->query( "SELECT * FROM jeux_combats");
while ($donnee = $result->fetch()) {
echo '<p>'.'le personnage'.$donnee['nom'].'a une force de'.$donnee['forceperso'].'</p>';
}
?>

Answer 1

Please read the manual: http://php.net/manual/en/pdo.construct.php
parameter: information about the database connection
parameter: username for the connection
parameter: password for the connection
parameter: a key=>value array of driver-specific connection options (optional)
It should be like this:
$dsn = 'mysql:dbname=testdb;host=127.0.0.1';
$user = 'dbuser';
$password = 'dbpass';
try {
$dbh = new PDO($dsn, $user, $password);
} catch (PDOException $e) {
echo 'Connection failed: ' . $e->getMessage();
}
About your second question. The error should disappear after you will fix your first problem. Anyways... You could check if $bdd is null or not if you fear that the second error could appear again even after you will fix your first problem. Something like:
if($bdd != null){
if($result = $bdd->query( "SELECT * FROM jeux_combats")){
while ($donnee = $result->fetch(PDO::FETCH_ASSOC)) {
echo '<p>'.'le personnage'.$donnee['nom'].'a une force de'.$donnee['forceperso'].'</p>';
}
}
}
The whole code in your case would be:
$dsn = 'mysql:dbname=testdb;host=127.0.0.1';
$user = 'dbuser';
$password = 'dbpass';
try {
$bdd = new PDO($dsn, $user, $password);
if($bdd != null){
if($result = $bdd->query( "SELECT * FROM jeux_combats")){
while ($donnee = $result->fetch(PDO::FETCH_ASSOC)) {
echo '<p>'.'le personnage'.$donnee['nom'].'a une force de'.$donnee['forceperso'].'</p>';
}
}
}
} catch (PDOException $e) {
echo 'Connection failed: ' . $e->getMessage();
}