How to create a static variable and call it from another class? - php

Question

I have a class called DB_Bookings, within that class I have a function called updated_variables() within this is a simple script to look at the date of a published post and change the name of a variable accordingly.
Doing this, throughout my app I intend to use the variable and it will change dynamically per post depending on the date created.
I am struggling to call the variables from within another class. Please see my working below:
class DB_Bookings {
...
public function updated_variables() {
global $post;
$compare_date = strtotime( "2018-05-22" );
$post_date = strtotime( $post->post_date );
if($compare_date > $post_date) {
$weddingNameVariable = 'db-bookingsweddingname';
...
} else {
$weddingNameVariable = 'weddingName';
}
}
} // end DB_Bookings class
Then in my other class (in a file called class-db-bookings-admin.php)
class DB_Bookings_Admin {
...
public function save_metabox( $post_id, $post ) {
...
update_post_meta( $post_id, DB_Bookings::updated_variables($weddingNameVariable), $db_bookingsnew_weddingname );
...
}
} // end Class DB_Bookings_Admin
The idea here is that I can echo out the variable set in my DB_Bookings class and it can change based on the post date (this is essentially compensating for legacy variables as I overhaul the coding of the app).
However, it doesn't appear to be saving and I'm getting the following error
[22-May-2018 19:29:43 UTC] PHP Notice: Undefined variable: weddingNameVariable in /var/www/html/wp-content/plugins/db-bookings/admin/class-db-bookings-admin.php on line 853

Answer 1

Another approach based on comments.
class WeddingVariables {
//add all of the variables needed to this class
//you could create getters/setters to manage this data
$variableA = "data";
//get the variable
public function get_variable_a() {
return $this->variableA;
}
//set the variable
public function set_variable_a( $value ) {
$this->variableA = $value;
}
}
//a global variable
$WeddingVariables = new WeddingVariables();
//admin class
class DB_Bookings_Admin {
public function save_metabox( $post_id, $post ) {
global $WeddingVariables; //now we can access this within this method
//get the value of a variable from the class
$someVariable = $WeddingVariables->get_some_variable();
}
}

Answer 2

All I'm seeing that you're missing here is declaring your variable and treating it as static within the class itself.
public static $weddingNameVariable;
if($compare....)
self::$weddingNameVariable;
That's the basic bit you'll want to change, but there's a somewhat more complicated bit that's not correct: you're treating a non-static function as if it's static. So you may need to change your updated_variables function to be static itself. I also see that you're trying to do $post->post_date immediately after declaring global $post; but without initializing it to have any value. If you are trying to access post data sent from the client, try $_POST['some-key-here'] which is defined by PHP and accessible anywhere.
Once that's all straightened out, you can either have your updated_variables function return the new value you've set, or call the function the line before and then access the variable using DB_Bookings::$weddingNameVariable.

Answer 3

I notice a couple of things here. First, updated_variables() is not a static method, although you are calling it as a static method DB_Bookings::updated_variables(). To use that method statically, you would need to make it a static method via public static function updated_variables(). That is a discussion in itself however.
There are many ways to accomplish what you want, but you could do it with a global variable.
<?php
//this is global
$weddingNameVariable = false;
class DB_Bookings {
public function updated_variables() {
global $weddingNameVariable;
//now you can read/update this variable from within this method
}
}
class DB_Bookings_Admin {
public function save_metabox( $post_id, $post ) {
global $weddingNameVariable;
//now you can read/update this variable from within this method.
}
}
This may not be the OOP approach you are looking for, as you could utilize a static variable, but if that value you needs to change often, you'd be better managing it via other options in my opinion.