Code Review: Sanity Checks

four.php

<?php

$logger = getLogger();
if (($logger instanceof Logger) == false) {
  exit(-1);
}

one.php

<?php

$people = getNumberOfPeople();
if ($people === null) {
  exit(-1);
}

// do numeric logic

three.php

<?php

$logger = getLogger();
if ($logger == null) {
  exit(-1);
}

two.php

<?php

$people = getNumberOfPeople();
if (is_numeric($people) == false) {
  exit(-1);
}

// do numeric logic