PHP : condition on a mysql db - php

Question

I'm pretty new in PHP coding, and I cannot find the error in the following code... could you help me please ?
Fatal error: Cannot use object of type PDOStatement as array in C:\wamp\www\membre\inscription_post.php on line 14 Call Stack # Time Memory Function Location 1 0.0006 682688 {main}( ) ..\inscription_post.php:0
<?php
try
{
$bdd = new PDO('mysql:host=localhost;dbname=test', 'root', '');
}
catch(Exception $e)
{
die('Erreur : '.$e->getMessage());
}
$mem = $bdd -> query('SELECT * FROM membres');
while ($data = $mem -> fetch())
{
if($mem['pseudo'] == $_POST['pseudo'])
{
echo "Pseudo existant";
}
else
{
$pass_hache = sha1($_POST['pass']);
$req = $bdd->prepare('INSERT INTO membres (pseudo, pass, email, date_inscription) VALUES(?, ?, ?, CURDATE())');
$req->execute(array($_POST['pseudo'], $pass_hache, $_POST['email']));
header('Location: inscription.php');
echo "Membre ajouté";
}
}
$mem -> closeCursor();
?>
membres table structure is the following
id(=INT, primary key),
pseudo (VARCHAR(255)),
pass (VARCHAR(255)),
date_inscription (date)
Thank you for your help

Answer 1

something like this
<?php
$dsn = 'mysql:host=localhost;dbname=test;charset=utf8';
$opt = array(
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC
);
$bdd = new PDO($dsn,'root','', $opt);
$stm = $bdd->prepare('SELECT 1 FROM membres WHERE pseudo=?');
$stm->execute(array($_POST['pseudo']));
$row = $stm->fetch();
if ($row) {
echo "Pseudo existant";
} else {
$pass_hache = sha1($_POST['pass']);
$sql = 'INSERT INTO membres VALUES(NULL, ?, ?, ?, CURDATE())';
$req = $bdd->prepare($sql);
$req->execute(array($_POST['pseudo'], $pass_hache, $_POST['email']));
header('Location: inscription.php');
}
insert query can be wrong, depends on the table schema

Answer 2

if($mem['pseudo'] == $_POST['pseudo'])
^^^--- should be $data instead
But this is bad code. You're basically buying up the entire contents of a grocery store (your members table), driving it all home, then throwing away everything EXCEPT the one chocolate bar you wanted. You should be doing this in the DB, essentially
SELECT * FROM members WHERE pseudo=...

Answer 3

if($mem['pseudo'] == $_POST['pseudo']) should be if($data['pseudo'] == $_POST['pseudo']) as you are reading each line from $mem as $data. However, this doesn't seem like the best option for doing what it looks like you are trying to do - why not search for $_POST['pseudo'] in the database directly instead of looping through them all?