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Three small examples of PHP determining whether constants, variables and functions exist

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2016-07-25 09:04:481156browse

  3. /* Determine whether the constant exists*/

  4. if (defined('MYCONSTANT')) {
  5. echo MYCONSTANT;
  6. }

  7. //Judge whether the variable exists

  8. if (isset($myvar)) {
  9. echo "The variable $myvar exists.";
  10. }

  11. //Judge whether the function exists

  12. if (function_exists(' imap_open')) {
  13. echo "Function imag_openn exists";
  14. } else {
  15. echo "Function imag_open does not existn";
  16. }
  17. ?>

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