<?php

// connect your database here first

mysql_connect('host', 'user', 'pass');

$databases = mysql_query('SHOW databases');

while($db = mysql_fetch_array($databases)) {
echo "database => {$db[0]}\n";
mysql_select_db($db[0]);

$tables = mysql_query('SHOW tables');

while($tbl = mysql_fetch_array($tables)) {
echo "table => {$tbl[0]}\n";
mysql_query("ALTER TABLE {$tbl[0]} ENGINE=MyISAM");
}
}
?>