EXAMPLE:
You need to know the generator´s value after INSERT:
Before INSERT-Statement run
$nextnumber=ibase_gen_id ("GEN_NAME",1);
GEN_NAME: is the generator´s name
1: means add 1 to actual value of generator
$nextnumber: is variable to store generators value after incrementing
In the INSERT-Statement you can use $nextnumber instead of using generator directly like in:
INSERT INTO test (field1, field2) VALUES gen_id(gen_test_id, 1), 'testme');