This PHP program demonstrates how to print all of the defined constants.

GetDefinedConstants.php

<?php

  // Two user-defined constants
  define("TRINITY", 3);
  define("APOSTLES", 12);

  $saaConstants = get_defined_constants(true);

  // Loop over each set of constants
  foreach($saaConstants as $sCategory => $saConstants) {

    // Make the category heading for each group of constants
    echo "<ul><h3>".$sCategory."</h3>";

    // Loop over the constants in the group
    foreach($saConstants as $sKey =>$sConstant) {
      echo "<li>".$sKey." => ".$sConstant."</li>";
    }
    echo "</ul>";
  }

?>

Output