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PHP - Data Types

PHP supports several data types, allowing for a wide range of operations and data manipulations. Understanding these data types is crucial for writing efficient and error-free code. Here’s a detailed overview of the data types in PHP:

1. Scalar Types

a. Boolean

A boolean represents two possible values: true or false.

Example:

php
<?php
        $flag = true;
        $isLoggedIn = false;
        ?>

b. Integer

An integer is a non-decimal number between -2,147,483,648 and 2,147,483,647 (on a 32-bit system).

Example:

php
<?php
        $number = 1234;
        $negativeNumber = -5678;
        ?>

c. Float (Double)

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

Example:

php
<?php
        $floatNumber = 1.234;
        $scientificNumber = 0.1234e4; // 1234
        ?>

d. String

A string is a sequence of characters.

Example:

php
<?php
        $text = "Hello, World!";
        $multilineText = "This is a
        multi-line string.";
        ?>

2. Compound Types

a. Array

An array stores multiple values in one single variable. Arrays can be indexed or associative.

Example:

php
<?php
        $indexedArray = array(1, 2, 3, 4);
        $associativeArray = array("name" => "John", "age" => 30);
        ?>

b. Object

An object is an instance of a class. Classes define the structure and behavior (data and functions) that the objects created from the class will have.

Example:

php
<?php
        class Car {
            public $color;
            public $model;
            public function __construct($color, $model) {
                $this->color = $color;
                $this->model = $model;
            }
            public function message() {
                return "My car is a " . $this->color . " " . $this->model . ".";
            }
        }
        
        $myCar = new Car("black", "Volvo");
        echo $myCar->message();
        ?>

3. Special Types

a. NULL

The NULL value represents a variable with no value assigned.

Example:

php
<?php
        $var = NULL;
        ?>

b. Resource

A resource is a special variable that holds a reference to an external resource, such as a database connection or a file.

Example:

php
<?php
        $file = fopen("test.txt", "r");
        ?>

Type Juggling

PHP is a loosely typed language, meaning it automatically converts variables to the appropriate data type depending on their value and the context in which they are used.

Example:

php
<?php
        $var = "3.14";
        echo $var + 2; // Output: 5.14
        ?>

Type Casting

You can explicitly convert a variable from one type to another using type casting.

Example:

php
<?php
        $var = "3.14";
        $floatVar = (float)$var;
        $intVar = (int)$var;
        echo $floatVar; // Output: 3.14
        echo $intVar; // Output: 3
        ?>

Checking Data Types

PHP provides several functions to check the type of a variable:

  • is_bool()
  • is_int()
  • is_float()
  • is_string()
  • is_array()
  • is_object()
  • is_null()

Example:

php
<?php
        $var = 42;
        if (is_int($var)) {
            echo "This is an integer.";
        }
        ?>

Summary

PHP supports several data types, including scalar types (boolean, integer, float, string), compound types (array, object), and special types (NULL, resource). Understanding these types and how to use them effectively is fundamental to writing robust PHP applications.