What is the proper way to declare variables in php?

Question

I was using variables in my php file without declaring them. It was working perfect in old version of localhost (i.e vertrigoServ 2.22).

But when I moved to latest version of localhost (i.e xampp 3.2.1), I encountered variables declaration warnings and errors something like this:

Notice: Undefined variable: att_troops_qty in D:\Installed Programs\htdocs\dashboard\WarLord\PHP_Code\MyAjax.php on line 1247

So I declared all the variables at the top of php file like this:

$page = "";
$att_troops_qty = "";
$def_troops_qty = "";
$ca_level = "";
$b_level = "";
$pre_buildings = "";
$created_pre_b = "";
$building_id = "";
$building_loc = "";
$ca_1_b_loc = "";
$ca_1_b_level = "";
$ca_2_b_loc = "";
$ca_2_b_level = "";

It solved the problem But I have confusion that this is not the proper way to declare variables.

Is there some more better way for variables declaration?

Answer 1

How you are declaring is perfectly alright and proper way.

$test = "";

or

$test = null;

these both are proper ways for declaring empty variables. for more info please visit http://php.net/manual/en/language.types.null.php

Answer 2

You need to declare variables before echoing them out. An example is here:

<?php
    $var = "test";
    echo $var; // it will echo out test
?>

And trying to echo out a variable this way will generate an error:

<?php
    echo $var; // it will generate error
    $var = "test";
?>

In addition, you can declare variables in another file and can include that file to echo out the variable somewhere. Remember to include the file first and then call it.

Example vars.php:

<?php
    // define vars
    $var1 = "Test 1";
    $var2 = "Test 2";
?>

Now in another file, include vars.php first and then call the variable:

<?php
    require_once"vars.php";
    echo $var1;
?>