Interview question

Explain polymorphism in PHP with an example. PHP में polymorphism एक उदाहरण के साथ समझाएं।

Answer

Short Answer

== (Equal) checks if two values are equal after performing "type juggling" (converting them to the same data type).
=== (Identical / Strict Equal) checks if two values are equal AND are of the exact same data type. It does NOT convert types.

Detailed Explanation & Code Example

In PHP, type juggling can lead to dangerous, unexpected bugs. It is a best practice to almost always use strict comparison (===).


$a = 5;      // Integer
$b = "5";    // String

// Loose Comparison (==)
if ($a == $b) {
    echo "True! PHP converted the string '5' to an integer for comparison.";
}

// Strict Comparison (===)
if ($a === $b) {
    echo "This will NOT execute.";
} else {
    echo "False! They look the same, but one is an Integer and one is a String.";
}

Common Pitfall Example

Consider the strpos() function, which returns the numeric index of a substring, or false if it's not found.


$str = "Hello World";
$position = strpos($str, "Hello"); // Returns 0 (index 0)

// BAD CODE: 0 == false is TRUE in loose comparison!
if ($position == false) {
    echo "Not found!"; // This incorrectly executes because 0 == false
}

// GOOD CODE: 0 !== false in strict comparison.
if ($position === false) {
    echo "Not found!";
}

Polymorphism का मतलब है same method नाम अलग-अलग class में अलग व्यवहार करता है। PHP में यह method overriding और interfaces से हासिल होता है।

interface Shape {
    public function area(): float;
}

class Circle implements Shape {
    public function __construct(private float $radius) {}
    public function area(): float { return pi() * $this->radius ** 2; }
}

class Rectangle implements Shape {
    public function __construct(private float $w, private float $h) {}
    public function area(): float { return $this->w * $this->h; }
}

function printArea(Shape $shape) {
    echo $shape->area();
}
printArea(new Circle(5));
printArea(new Rectangle(4, 6));

printArea() फंक्शन को फर्क नहीं पड़ता कौन सा shape मिला - वह सिर्फ area() call करता है, और हर class अपना implementation देती है। यही polymorphism है।

इंटरव्यू टिप: बताएं इस design से बाद में नया shape (जैसे Triangle) बिना printArea() बदले जोड़ा जा सकता है - Open/Closed Principle।

Was this answer clear?

Subjects

Short Answer

Detailed Explanation & Code Example

Common Pitfall Example

Related questions