It looks like he did it in the code he posted, in the first section here:
NewPing sonar[SONAR_NUM] = { // Sensor object array.
NewPing(4, 5, MAX_DISTANCE), // Each sensor's trigger pin, echo pin, and max distance to ping.
NewPing(6, 7, MAX_DISTANCE),
NewPing(8, 9, MAX_DISTANCE)
};
If your typical array looks like this:
int X[] = { 0, 5, 3, ect};
He simply put each variable on a separate line, like this:
int X[] = {
0,
5,
3,
ect
};
So if you did it the typical way you see arrays, it would look something like this, which is a bit harder to read:
NewPing sonar[SONAR_NUM] = { NewPing(4, 5, MAX_DISTANCE), NewPing(6, 7, MAX_DISTANCE), NewPing(8, 9, MAX_DISTANCE) };
Correct me if I'm wrong @david_2018