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

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Release: 2016-07-25 09:04:48
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  1. /* Determine whether the constant exists*/

  2. if (defined('MYCONSTANT')) {
  3. echo MYCONSTANT;
  4. }

  5. //Judge whether the variable exists

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

  9. //Judge whether the function exists

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

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