How-to make you don't forget to comment your code.

step1-comment-as-pseudocode.php

// create array for hold all dogs data

// just loop by get data from getNames()
// getNames() is generator so it's simple loop
// and we just need 5 dogs only
// each dog will name as value

// echo all dogs as json

step2-write-code-follow-comment.php

// create array for hold all dogs data
$dogs = [];

// just loop by get data from getNames()
// getNames() is generator so it's simple loop
// and we just need 5 dogs only
foreach(getNames(5) as $name) {
  // each dog will name as value
  $dogs[] = $name;
}

// echo all dogs as json
echo json_encode($dogs);