PHP Data Types

PHP Data Types & Type System

PHP supports 8 primitive data types categorized into Scalar, Compound, and Special types. Starting with PHP 8, PHP features a strong type system with explicit type hints, union types, and nullable types.

Categories of Data Types

flowchart TD
    A["PHP Data Types"] --> B["Scalar Types (Single Value)"]
    A --> C["Compound Types (Multiple Values)"]
    A --> D["Special Types"]
    B --> B1["string"] & B2["int"] & B3["float / double"] & B4["bool"]
    C --> C1["array"] & C2["object"] & C3["callable"] & C4["iterable"]
    D --> D1["null"] & D2["resource"]

Type Checking and Casting

// Check data type
gettype($val);
is_int($val);
is_string($val);
is_array($val);

// Explicit Type Casting
$count = (int)"42";
$price = (float)"19.99";
$isMember = (bool)1;

Practical Code Example (PHP 8 Typed Code)

<?php
declare(strict_types=1);

class UserProfile
{
    public function __construct(
        public string $username,
        public int $age,
        public float $rating,
        public bool $isActive,
        public ?string $bio = null // Nullable type
    ) {}
}

// Creating Compound Object Data Type
$user = new UserProfile("maksudur", 28, 4.95, true, "Senior Software Architect");

// Array (Compound Type)
$skills = ["PHP 8", "Laravel", "MySQL", "Docker"];

// Resource (Special Type)
$fileResource = fopen(__FILE__, "r");

echo "Username Type: " . gettype($user->username) . "
";
echo "Age Type: " . gettype($user->age) . "
";
echo "Skills Type: " . gettype($skills) . "
";
echo "File Resource Type: " . gettype($fileResource) . "
";

fclose($fileResource);

Best Practices

• Always Enable Strict Type Checking: Include declare(strict_types=1); at top of files to prevent unintended implicit type coercion.
• Use Nullable Types ?type and Union Types typeA|typeB: Explicitly declare when parameters or returns can accept null or multiple distinct types.
• Use var_dump() or get_debug_type() for Debugging: get_debug_type() in PHP 8 gives precise class names and type details.

Self-Check Challenge

Create a function processScore(int|float $score): string that uses PHP 8 union types to accept either an integer or float score and returns "Passed" if score >= 50!