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Variable in PHP

Variables are used for storing 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.
The correct way of declaring a variable in PHP:

$var_name = value;

Let's try creating a variable containing a string, and a variable containing a number:

$txt="Hello World!";
Naming Rules for Variables

A variable name must start with a letter or an underscore "_"
A variable name can only contain alpha-numeric characters and underscores (a-z, A-Z, 0-9, and _ )
A variable name should not contain spaces. If a variable name is more than one word, it should be separated with an underscore ($my_string), or with capitalization ($myString)

PHP Variables Scope

In PHP, variables can be declared anywhere in the script.
The scope of a variable is the part of the script where the variable can be referenced/used.
PHP has three different variable scopes:

Local and Global Scope

A variable declared outside a function has a GLOBAL SCOPE and can only be accessed outside a function.A variable declared within a function has a LOCAL SCOPE and can only be accessed within that function.
The following example tests variables with local and global scope:

$x=15; // global scope
function Test()
$y=100; // local scope
echo "<p> variables inside the function:</p>";
echo "Variable x is: $x";
echo "<br>";
echo "Variable y is: $y";
echo "<p>Test variables outside the function:</p>";
echo "Variable x is: $x";
echo "<br>";
echo "Variable y is: $y";

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