Restrict quantity of things in array

I need assistance limiting the quantity of things saved in an array. It must be in an ‘if’ assertion. Mainly it must depend an array and if it is at a sure restrict, do not permit any extra gadgets to be saved in it.

if (depend($array) < 3) {
  // let extra gadgets within the array
} else if (depend($array) = 3) {
  // do not let any extra gadgets within the array
}

Any and all assistance is at all times appreciated.