I. Variable in PHP

Variables in PHP start with a dollar sign ($) followed by the name of the variable.

A variable name

  • must start with a letter or the underscore character.
  • can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ ).
  • is case-sensitive ($name and $NAME are two different variables).
$abc = 12;

To check if a variable is defined, we can use (isset($name))

II. Variable types

There are 8 variable types in PHP, and you don’t have to declare variable types when creating a variable.

  • String
  • Integer
  • Float
  • Boolean
  • Null
  • Array
  • Object
  • Resource
$name = "Anna";
$age = 30;
$isFemale = true;
$height = 1.6;
$salary = null;

To display a structure of a variable including its type and value, we use var_dump().

// Print the whole variable
var_dump($name, $age, $isMale, $height, $salary);

// Result: string(4) "Anna" int(30) bool(true) float(1.600000000000000088817841970012523233890533447265625) NULL

III. Check variable types

To check type of a variable, we use gettype().

echo gettype($name) . '<br>';


// Print types of the variables
echo gettype($name) . '<br>';
echo gettype($age) . '<br>';
echo gettype($isFemale) . '<br>';
echo gettype($height) . '<br>';
echo gettype($salary) . '<br>';

IV. Variable scopes

1. Global scope

A variable declared outside a function has a GLOBAL SCOPE and can only be accessed outside a function:

$x = 5; // global scope

function count() {
  // using x inside this function will generate an error
  echo "<p>Variable x is: $x</p>";

echo "<p>Variable x is: $x</p>";

2. Local scope

A variable declared within a function has a LOCAL SCOPE and can only be accessed within that function:

function count() {
  $x = 5; // local scope
  echo "<p>Variable x is: $x</p>";

// using x outside the function will generate an error
echo "<p>Variable x is: $x</p>";