The method isReadOnly() reads a provided SQL statement for elements that might cause a read-write process to be created. The method is used internally by the load balancer to determine if a statement needs to be executed on the primary server but can also be called manually.

/*
* connection to load balancer assumed
*/
 
$SQL = "SELECT * FROM employees";
 
print $db->isReadOnlySql($SQL);
 
/*
* Returns false
*/
 
SQL = "SELECT * FROM employees FOR UPDATE";
 
print $db->isReadOnlySql($SQL);
 
/*
* Returns true
*/