Variable and Variable Scope

Variables:
Variables are used for storing a values, like text strings, numbers or arrays. When a variable is declared, it can be used over and over again in your script. All variables in PHP start with a ‘$’sign symbol.

$var_name=value;

For example:
<?php
$txt=”Hello world”;
echo $txt;
?>

Variable Scope:
The scope of a variable in PHP is the context in which the variable was created, and in which it can be accessed. Essentially, PHP has 2 scopes:
Global:
    The variable is accessible from anywhere in the script

Local:
    The variable is only accessible from within the function (or method) that created it.

Variable scope — and, in particular, local scope — make your code easier to manage. If all your variables are global, they can be read and changed from anywhere in your script. This can cause chaos in large scripts as many different parts of the script attempt to work with the same variable. By restricting a variable to local scope, you limit the amount of code that can access that variable, making your code more robust, more modular, and easier to debug.

For example:
<?php

$globalName = "Zoe";
function sayHello() {
  $localName = "Harry";
  echo "Hello, $localName!<br>";
}
sayHello();
echo "The value of \$globalName is: '$globalName'<br>";
echo "The value of \$localName is: '$localName'<br>";

?>

Output:
Hello, Harry!
The value of $globalName is: 'Zoe'
The value of $localName is: ''