$fnExecute provides a handle to a function that overrides the execute() function. The function should accept 3 parameters

• An object containing the connection
• The SQL statement
• The bind variables

Execute returns the result of the override function.

function overrideExecute($db,$sql,$var)
{
    return 'Hello World';
}
 
$db->fnExecute = 'overrideExecute';
 
$sql = 'select * from customers';
 
$result = $db->execute($sql);
 
print $result;
 
/*
* prints 'Hello World'
*/

The variable fnCacheExecute provides the same functionality as fnExecute but against the cacheExecute() method