Understanding the phototransistor
This image presents normal useful voltage polarities and current directions for NPN transistor in a circuit:

I guess you know that base current can be increased by reducing the resistance R1 or by increasing the voltage of BAT1.
The collector current in a loop which contains a voltage source BAT2, a load and the BE-section of transistor Q1, can be controlled by changing the current in the base loop.
Normally the collector current can be tens or hundreds times bigger than the base current due the current gain in the transistor, but not higher than the voltage of BAT2 and the resistance of the load allow by Ohm's law.
Think that in phototransistor light (actually carrier generation in the semiconductor molecular structure caused by photons) replaces the base current, there's no need for the base current loop.
I do not recommend a beginner starts to keep a circuit which has photodiode and ordinary transistor as an exact equivalent of phototransistor. The latter is probably designed for certain performance which is difficult to achieve by connecting a photodiode and ordinary transistor and simply the light affects to the parts of a specially shaped transistor, there's no separate photodiode in a phototransistor.
In addition too well adopted not so accurate equivalent circuit can harm learning the real semiconductor physics of the operation of a component, if he one day starts semiconductor engineering studies.