Update_time ?

<?PHP
 
include ('acces_a_la_DB.php');
$table = "table_concernee";

$req = mysql_query("SHOW TABLE STATUS FROM $table LIKE Update_time") or die ("ca marche pas");
echo "$req";

?>

<?php
// connexion base de données

$table = "ta_table";
$sql = "SHOW TABLE STATUS LIKE '$table'";

$req = mysql_query($sql) or die('Erreur SQL !<br>'.$sql.'<br>'.mysql_error());
$data = mysql_fetch_array($req);
$derniere_modif = $data['Update_time'];
mysql_close();

echo $derniere_modif;
?>