PHP Use static variable in other variable in class

Question

I have a minor problem with using a global variable class for my PHP app. I really want to use this method of storing variables because I know I'll be changing file names and folder structures as time goes on.

I want to use the variable public $rootin the variables under it, that aren't in a method.

Like this:

public $root = "/rootfolder/";
public $something = $root . "path/";

But I keep getting this error:

Fatal error: Constant expression contains invalid operations in C:_server\htdocs\p\chestools\core\php\global.php on line 26

Here's my full page:

class gvars {

  public static $debug_mode = true;

  /*
  * Tab Title Control
  * n\a
  */
  public static $tab_after                = " | Chestools";
  public static $tab_name_enable          = true;

  /*
  * Dialouge Control
  * utils.dialouges.php
  */
  public static $dia_show_fatal = true;
  public static $dia_enabled = true;

  /*
  * Page Paths
  * n\a
  */
  public static $root                     = "/p/chestools/";
  public static $path_home                = "Home";
  public static $path_contactus           = "Contactus";
  public static $path_login               = "Login";
  public static $path_signup              = "Signup";
  //General Pages
  public static $path_help                = "Help";
  public static $path_profile             = "Profile";
  //Student Pages
  public static $path_select_cat          = "Catagorys";
  //Teacher Pages
  public static $path_view_student        = "View";
  public static $path_create              = "Create";
  //Catagorys
  public static $path_cat_math            = "c/math/";
  public static $path_cat_life_sci        = "c/life-science/";
  public static $path_cat_int_sci         = "c/interactive-science/";
  public static $path_cat_earth_sci       = "c/earth-science/";
  //Security
  public static $path_sec_finish          = "security/Finish";
  public static $path_sec_change_password = "security/ChangePassword";
  public static $path_sec_change_email    = "security/ChangeEmail";
  public static $path_sec_checkpoint      = "security/Checkpoint";

  /*
  * System Paths
  * n\a
  */
  public static $head_css                 = "core/css/chestools.css";
  public static $head_js_app              = "core/js/app.js";

  /*
  * Footer Resource Paths
  * n\a
  */
  public static $path_dwa                 = "about/district-wide-accounts/";
  public static $path_isa                 = "about/independent-school-          accounts/";
  public static $path_support             = "support/";
  public static $path_pp                  = "Privacy";
  public static $path_tos                 = "Terms";

}

Cannot reproduce in 5.0.0 - 5.6.26, hhvm-3.10.0 - 3.14.4, 7.0.0 - 7.1.0RC3 — Gordon
– Gordon, Commented Sep 30, 2016 at 15:35

Anass · Accepted Answer · 2016-09-30 02:03:51Z

0

This seems you are using a PHP version less than the 5.6

If you want really concatenate content in a property initialization, you can do it through the __construct() function

PHP Versions Before 5.6

Check out the following link in the PHP Manual for Property declarations.

...This declaration may include an initialization, but this initialization must be a constant value--that is, it must be able to be evaluated at compile time and must not depend on run-time information in order to be evaluated.

PHP 5.6

PHP 5.6 onwards, you can use concatenation when declaring default class properties in PHP.

answered Sep 30, 2016 at 2:03

Anass

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4 Comments

Jacob Jewett Over a year ago

last time i checked my php version, it was 5.6.21.

Anass Over a year ago

Can you please tell us what is the content of the line 26 of your code?

Jacob Jewett Over a year ago

public static $path_home = "Home";

Anass Over a year ago

Please check out this answer, this is a possible form to access global variables from within class context. stackoverflow.com/a/4489351/6366593

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