$annonce_id = getValueFromQuery(sprintf("SELECT annonce_id FROM ".$cfg_prefixe."annonces WHERE annonce_user_id = '%s' ORDER BY annonce_datetime DESC LIMIT 1", 
			mysql_real_escape_string($user_id)));

$annonce_id = getValueFromQuery(sprintf("SELECT MAX(annonce_id) as annonce_id FROM ".$cfg_prefixe."annonces WHERE annonce_user_id = '%s'", 
			mysql_real_escape_string($user_id)));

CREATE TABLE `annonces` (
`annonce_id` int(11) NOT NULL auto_increment,
`annonce_user_id` int(11) NOT NULL,
`annonce_datetime` datetime NOT NULL,
`annonce_statut` tinyint(4) NOT NULL,
`annonce_position` tinyint(4) NOT NULL,
`annonce_views` int(11) NOT NULL,
`annonce_type` enum('vente','location') NOT NULL,
`annonce_type_bien` enum('appartement','maison') NOT NULL,
`annonce_address` text NOT NULL,
`annonce_zipcode` varchar(10) NOT NULL,
`annonce_city` text NOT NULL,
`annonce_country` int(11) NOT NULL,
`annonce_surface` float NOT NULL,
`annonce_rooms` int(11) NOT NULL,
`annonce_price` float NOT NULL,
`annonce_description` text NOT NULL,
`annonce_old_price` float NOT NULL,
PRIMARY KEY (`annonce_id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=12 ;

<?php
$time_start = microtime(true);

// Là tu mets ton code PHP à exécuter

$time_end = microtime(true);
$time = $time_end - $time_start;

print "Exécuté en ".$time." secondes";
?>