Data Types (string, integer, float, boolean, array, object, NULL)

• In PHP, a data type defines the type of value a variable can hold.
• PHP is loosely typed → You don’t need to declare the type of variable (like int, string) before using it. PHP automatically assigns a type depending on the value.

Example:

<?php
$x = 10;        // integer
$y = "Hello";   // string
$z = 10.5;      // float
?>

• gettype($var) → returns type as string
• You can check the type using:
• var_dump($var) → shows type + value

1. String:

• A string is a sequence of characters inside single quotes (‘ ‘) or double quotes (” “).
• Strings can contain letters, numbers, spaces, and special characters.
• In double quotes, variables are parsed (expanded). In single quotes, they are not.

Example:

<?php
$name = "Alice";
$greeting1 = "Hello, $name";   // variable is expanded
$greeting2 = 'Hello, $name';   // variable is not expanded

echo $greeting1;  // Output: Hello, Alice
echo "<br>";
echo $greeting2;  // Output: Hello, $name
?>

2. Integer:

• An integer is a whole number (no decimal point).
• It can be positive, negative, or zero.
• Range depends on system (usually 64-bit).

Example:

<?php
$a = 42;        // positive integer
$b = -15;       // negative integer
$c = 0;         // zero

echo gettype($a); // Output: integer
?>

3. Float (Double / Real Numbers):

• A float is a number with a decimal point or in exponential form.

Example:

<?php
$pi = 3.14159;
$price = 99.99;
$exp = 1.2e3;  // 1200 (exponential notation)

echo var_dump($pi);   // float(3.14159)
echo "<br>";
echo var_dump($exp);  // float(1200)
?>

4. Boolean:

• A boolean has only two possible values:
  • true (1)
  • false (0)
• Used for conditions and comparisons.

Example:

<?php
$is_admin = true;
$is_logged_in = false;

echo var_dump($is_admin);      // bool(true)
echo "<br>";
echo var_dump($is_logged_in);  // bool(false)

if($is_admin){
  echo "Welcome, Admin!";
}
?>

5. Array:

• An array stores multiple values in a single variable.
• Types of arrays:
  1. Indexed Array → Numeric keys (0,1,2…)
  2. Associative Array → Named keys (like dictionary)
  3. Multidimensional Array → Array inside an array.

Example:

<?php
// Indexed array
$colors = ["red", "green", "blue"];

// Associative array
$student = ["name" => "John", "age" => 21, "grade" => "A"];

// Multidimensional array
$matrix = [
  [1,2,3],
  [4,5,6],
  [7,8,9]
];

echo $colors[0];  // Output: red
echo "<br>";
echo $student["name"]; // Output: John
echo "<br>";
echo $matrix[1][2]; // Output: 6
?>

6. Object:

• An object is an instance of a class.
• A class is a blueprint, and objects are created from it.

Example:

<?php
class Car {
  public $brand;
  public $color;

  function __construct($brand, $color){
    $this->brand = $brand;
    $this->color = $color;
  }

  function display(){
    return "Car: $this->brand, Color: $this->color";
  }
}

$car1 = new Car("Toyota", "Red");
echo $car1->display();   // Output: Car: Toyota, Color: Red
?>

7. NULL:

• NULL is a special type that represents a variable with no value.
• Used to reset a variable or mark “empty”.
• NULL is different from an empty string ("") or zero (0).

Example:

<?php
$x = "Hello";
$x = null;

var_dump($x); // NULL
?>

8. Resource (Special Type):

• A resource is a special variable that holds a reference to an external resource (like database connection, file handle).
• Example: MySQL connection, file opened with fopen().

Example:

<?php
$file = fopen("test.txt", "r");
var_dump($file);   // resource(type=stream)
fclose($file);
?>