PHP Data Types

PHP supports 10 different data types, each designed for specific kinds of information. Understanding data types is crucial for writing efficient and bug-free code. Let's explore each type and learn when to use them!

PHP Data Types Overview

PHP organizes its data types into three categories:

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Scalar Types (Single Values)

1. Integer (int)

Whole numbers without decimal points, positive or negative:

<?php
$age = 25;           // Positive integer
$temperature = -10;  // Negative integer
$hex = 0xFF;         // Hexadecimal (255)
$octal = 0755;       // Octal (493)
$binary = 0b1010;    // Binary (10)
?>

2. Float (double)

Numbers with decimal points or in exponential form:

<?php
$price = 19.99;
$pi = 3.14159;
$scientific = 1.5e3;  // 1500
$negative = -2.5;
?>

3. String

Sequence of characters enclosed in quotes:

<?php
$single = 'Single quotes';
$double = "Double quotes";
$name = "John";
$greeting = "Hello, $name!";  // Variable parsing
?>

4. Boolean (bool)

Represents true or false:

<?php
$isActive = true;
$isDeleted = false;

// These values are considered false:
// false, 0, 0.0, "", "0", [], null

// Everything else is true
?>

Compound Types (Multiple Values)

5. Array

Ordered collection of values:

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

// Associative array
$person = [
    "name" => "John",
    "age" => 30,
    "city" => "New York"
];

// Mixed array
$mixed = [1, "text", true, [1, 2, 3]];
?>

6. Object

Instances of classes:

<?php
class Person {
    public $name;
    public $age;
}

$user = new Person();
$user->name = "John";
$user->age = 30;
?>

7. Callable

Functions that can be called:

<?php
function greet($name) {
    return "Hello, $name!";
}

$callback = 'greet';
echo $callback("John");  // Calls greet("John")
?>

8. Iterable

Arrays or objects that can be iterated (PHP 7.1+):

<?php
function process(iterable $items) {
    foreach ($items as $item) {
        echo $item;
    }
}

process([1, 2, 3]);  // Works with arrays
?>

Special Types

9. Resource

References to external resources (files, databases):

<?php
$file = fopen("data.txt", "r");  // File resource
// $db = mysqli_connect(...);    // Database resource
fclose($file);
?>

10. NULL

Represents a variable with no value:

<?php
$empty = null;
$undefined;  // Also NULL

// These create NULL:
$var = null;
unset($var);
$notSet;
?>

Type Checking Functions

PHP provides functions to check variable types:

<?php
$age = 25;

if (is_int($age)) {
    echo "Age is an integer";
}

// Get type as string
echo gettype($age);  // Output: "integer"
?>

Common Mistakes

<?php
$a = 0.1 + 0.2;
$b = 0.3;

if ($a == $b) {  // ❌ May fail due to precision
    echo "Equal";
}

// ✅ Correct way
if (abs($a - $b) < 0.0001) {
    echo "Equal (within tolerance)";
}
?>

<?php
$str = "0";
$num = 0;

if ($str == $num) {  // ✅ true (type juggling)
    echo "Equal with ==";
}

if ($str === $num) {  // ❌ false (different types)
    echo "This won't print";
}
?>

Summary

What's Next?

Now that you know PHP's data types, let's explore Type Juggling - PHP's automatic type conversion system. You'll learn how PHP converts between types and when to use explicit type casting!