PHP mysql_query inside FOR only works first loop - php

Question

I´m trying to update some different registers in a mysql database sending the commands from a FOR loop in php, but the query is only done the 1st loop. Here´s the code:
$conexion = mysql_connect($hostname, $user, $pass) or die ("Error establishing connection with the Database");
mysql_select_db($db,$conexion) or die("Error selecting the Database");
$j=0;
for ($i=0;$i<count($notifs);$i++){
$sql="UPDATE tef SET notif='$notifs[$i]' WHERE sn_rec='$unsersn_recs[$j]';";
echo $sql."<br>";
$res=mysql_query($sql, $conexion) or die (mysql_error());
$j++;
}
mysql_close($conexion);
The query text is correctly done (the echo shows the different lines created), but the changes in the database are done only in the 1st loop (1st query) and I don´t receive any error. What may I be missing?
Thanks in advance!

Answer 1

This is wonderful example where you should use prepared statements.
I give you an example which is also secure against SQL injections.
$mysqli = new mysqli($hostname, $user, $pass, $db);
if (mysqli_connect_errno()) {
die("Error establishing connection!");
}
$stmt = $mysqli->prepare("UPDATE tef SET notif=? WHERE sn_rec=?");
$j=0;
for ($i=0;$i<count($notifs);$i++) {
$stmt->bind_param('ii', $notifs[$i], $unsersn_recs[$j]);
$stmt->execute();
if(!empty($stmt->error)) echo $stmt->error;
$j++;
}
$stmt->close();
$mysqli->close();
Hint: If notif or sn_rec are varchar/text types, just replace the 'i' with a 's' in bind_param().