<?php

$flip = array('even' => 'odd', 'odd' => 'even');
$class = 'even';

$time_start = microtime(true);
for ($number = 0; $number < 200000; $number++) {
  $class = ($number % 2 == 1) ? 'even': 'odd';
}
$time_end = microtime(true);
$old_time = $time_end - $time_start;

$time_start = microtime(true);
for ($number = 0; $number < 200000; $number++) {
  $class = $flip[$class];
}
$time_end = microtime(true);
$array_flip_time = $time_end - $time_start;

$time_start = microtime(true);
for ($number = 0; $number < 200000; $number++) {
  $class = $class == 'even' ? 'odd' : 'even';
}
$time_end = microtime(true);
$tri_flip_time = $time_end - $time_start;

echo "Old time is $old_time seconds\n";
echo "Array flip time is $array_flip_time seconds\n";
echo "Trinary flip time is $tri_flip_time seconds\n";
?>

/**
Results:
//
Old time is 2.94821381569 seconds
Array flip time is 2.82611393929 seconds
Trinary flip time is 3.10265183449 seconds
//
Old time is 2.9622759819 seconds
Array flip time is 2.9366338253 seconds
Trinary flip time is 3.28688883781 seconds
//
Old time is 3.1440680027 seconds
Array flip time is 2.91075491905 seconds
Trinary flip time is 3.05684518814 seconds
//
Old time is 3.09293603897 seconds
Array flip time is 2.87835907936 seconds
Trinary flip time is 3.03077507019 seconds
//
Old time is 3.16652011871 seconds
Array flip time is 2.86847901344 seconds
Trinary flip time is 3.02843999863 seconds
*/