Introduction: Why PHP Data Types Matter

In PHP, data types define the kind of data a variable can store, such as text, numbers, or more complex structures like arrays and objects. While PHP is a loosely typed language, meaning you don’t need to declare data types explicitly, understanding how they work is crucial.

Why? Because:

• It helps you write better, bug-free code

• It ensures correct data manipulation

• It makes you more confident with type conversions, comparisons, and validations

This article walks you through PHP's eight data types, with real-world examples, a comparison table, and tips to avoid common mistakes.

PHP Data Types Overview

PHP has 8 primary data types, grouped into three categories:

✍️ Scalar Data Types

✅ 1. String

A sequence of characters enclosed in single or double quotes.

<?php
$name = "John Doe"; // String variable
echo "Hello, " . $name;
?>

✅ 2. Integer

Whole numbers, positive or negative, without decimals.

$age = 30; // Integer

✅ 3. Float (Double)

Numbers with decimal points.

$price = 49.99; // Float

✅ 4. Boolean

Represents true or false.

$isLoggedIn = true;

Compound Data Types

✅ 5. Array

A variable that holds multiple values.

$colors = array("Red", "Green", "Blue");
// Access with index
echo $colors[0]; // Red

✅ 6. Object

An instance of a user-defined class.

class Car {
    public $brand = "Toyota";
}
$myCar = new Car();
echo $myCar->brand; // Toyota

Special Data Types

✅ 7. NULL

A variable with no value.

$deletedUser = NULL;

✅ 8. Resource

A reference to an external resource (like a file or database connection).

$handle = fopen("data.txt", "r"); // File resource

Comparison Table: PHP Data Types

Complete Example Using All PHP Data Types

<?php
// Scalar Types
$name = "Alice";            // String
$age = 25;                  // Integer
$height = 5.7;              // Float
$isStudent = true;          // Boolean

// Compound Types
$subjects = array("Math", "Science", "PHP"); // Array

class Student {
    public $university = "StudyZone University";
}
$student = new Student();  // Object

// Special Types
$project = NULL;           // NULL
$file = fopen("sample.txt", "r"); // Resource

// Output
echo "Name: $name<br>";
echo "Age: $age<br>";
echo "Height: $height ft<br>";
echo "Student: " . ($isStudent ? "Yes" : "No") . "<br>";
echo "Subjects: " . implode(", ", $subjects) . "<br>";
echo "University: " . $student->university . "<br>";
?>

⚠️ Tips & Common Pitfalls

✅ Best Practices

• Use gettype($variable) or var_dump($variable) to inspect types.

• Prefer explicit casting when needed: (int)$price

• Use strict comparison (===) to avoid type juggling bugs.

❌ Common Mistakes

• Assuming "5" + 5 results in string—it actually returns 10 (auto-casting)

• Forgetting NULL values can affect conditions (if ($var) is false if null)

• Confusing == with === when comparing values

Type Casting in PHP

You can convert between types manually:

$number = "10";        // String
$converted = (int)$number; // Integer

Conclusion: Master the Foundation

Understanding PHP data types is foundational for everything else you'll build. Whether you’re validating forms, creating APIs, or working with databases—knowing what type your data is, and how PHP treats it, is vital.