$nombre_remarques = mysql_query('SELECT for, num_com FROM commentaires_com WHERE for="par" AND num_com="41275"') or die( 'Erreur MySQL nb rem : <br />'.mysql_error() );
$nombre_remarques_final = mysql_num_rows($nombre_remarques);

echo 'SELECT for, num_com FROM commentaires_com WHERE for="par" AND num_com="41275"';

SELECT for, num_com FROM commentaires_com WHERE for="par" AND num_com="41275"

Erreur MySQL nb rem :
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'for, num_com FROM commentaires_com WHERE for="par" AND num_com="41275"' at line 1

CREATE TABLE `commentaires_com` (
`id` int(3) NOT NULL auto_increment,
`for` varchar(10) NOT NULL,
`valide` int(1) NOT NULL default '0',
`num_com` varchar(10) NOT NULL,
`commentaire` text NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB ;

Edit : grrrrrr, Cyrano je t'aurais