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wbcarts at juno dot com
5 years ago
11/14/2016 - note updated by sobak
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CONSTANTS and PHP Class Definitions

Using "define('MY_VAR', 'default value')" INSIDE a class definition does not work as expected. You have to use the PHP keyword 'const' and initialize it with a scalar value -- boolean, int, float, string (or array in PHP 5.6+) -- right away.

<?php

define
('MIN_VALUE', '0.0');   // RIGHT - Works OUTSIDE of a class definition.
define('MAX_VALUE', '1.0');   // RIGHT - Works OUTSIDE of a class definition.

//const MIN_VALUE = 0.0;         RIGHT - Works both INSIDE and OUTSIDE of a class definition.
//const MAX_VALUE = 1.0;         RIGHT - Works both INSIDE and OUTSIDE of a class definition.

class Constants
{
 
//define('MIN_VALUE', '0.0');  WRONG - Works OUTSIDE of a class definition.
  //define('MAX_VALUE', '1.0');  WRONG - Works OUTSIDE of a class definition.

 
const MIN_VALUE = 0.0;      // RIGHT - Works INSIDE of a class definition.
 
const MAX_VALUE = 1.0;      // RIGHT - Works INSIDE of a class definition.

 
public static function getMinValue()
  {
    return
self::MIN_VALUE;
  }

  public static function
getMaxValue()
  {
    return
self::MAX_VALUE;
  }
}

?>

#Example 1:
You can access these constants DIRECTLY like so:
* type the class name exactly.
* type two (2) colons.
* type the const name exactly.

#Example 2:
Because our class definition provides two (2) static functions, you can also access them like so:
* type the class name exactly.
* type two (2) colons.
* type the function name exactly (with the parentheses).

<?php

#Example 1:
$min = Constants::MIN_VALUE;
$max = Constants::MAX_VALUE;

#Example 2:
$min = Constants::getMinValue();
$max = Constants::getMaxValue();

?>

Once class constants are declared AND initialized, they cannot be set to different values -- that is why there are no setMinValue() and setMaxValue() functions in the class definition -- which means they are READ-ONLY and STATIC (shared by all instances of the class).

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