我可以通过PHP中的变量将DEFINED常量传递给函数吗？

Question

I have the following code:

DEFINE('DEFINEDTESTVAR', 'Hello World');

function callit($callVar) {
  echo "The call is ".$callVar;
}


$passthis = 'DEFINEDTESTVAR';
callit($passthis);

I know I can do callit(DEFINEDTESTVAR) but that's not what I am looking to do. Is it possible?

Answer 1

Either pass the constant itself:

$passthis = DEFINEDTESTVAR;

Or access it through constant() which allows you to test for null in case it isn't defined (for undefined constants, passing the constant literally results in a string with the constant name):

$passthis = constant('DEFINEDTESTVAR');

Answer 2

define('DEFINEDTESTVAR', 'Hello World'); // you should use define

function callit($callVar) {
  echo "The call is ".$callVar;
}    

$passthis = DEFINEDTESTVAR; // no need to use quotes
callit($passthis);

Answer 3

You can get a constant's value from a string with constant(). It will return null if the named constant is not found.

$passthis = constant('DEFINEDTESTVAR');
callit($passthis);

Answer 4

<?php 
DEFINE('DEFINEDTESTVAR', 'Hello World');

function callit($callVar) {
  echo "The call is ".$callVar;
}


$passthis = DEFINEDTESTVAR;
callit($passthis);