Comparison Operators in PHP: A Complete Guide

Overview

Comparison operators are fundamental in PHP, enabling developers to make decisions by comparing variables. This guide discusses the intricacies of these operators with practical examples.

Equality and Identity

In PHP, == checks if two values are equal, while === checks if they are identical in value and type. For example:

$x = 5;
$y = '5';
var_dump($x == $y);  // bool(true)
var_dump($x === $y); // bool(false)

This shows that while $x and $y are equal in value, they are not identical since one is a string and the other is an integer.

Inequality and Non-identity

Similar to equality, != or <> checks for inequality, and !== checks for non-identity. Here’s how they work:

$x = 10;
$y = '10';
var_dump($x != $y);  // bool(false)
var_dump($x !== $y); // bool(true)

Greater Than and Less Than

Operators > and < are straightforward; they compare numbers:

$x = 5;
$y = 10;
var_dump($x < $y);   // bool(true)
var_dump($x > $y);   // bool(false)

Combined Operators

PHP 7 introduced the spaceship operator <=>, which returns 0 if values on either side are equal, a negative number if the left is less, or a positive number if the left is greater. Here’s how it’s used:

$x = 5;
$y = 5;
var_dump($x <=> $y);  // int(0)
$x = 2;
$y = 5;
var_dump($x <=> $y);  // int(-3)
$x = 10;
$y = 5;
var_dump($x <=> $y);  // int(1)

Truth-Value Testing

PHP’s loose typing means == can yield surprising results:

$x = 0;
$y = 'hello';
var_dump($x == $y);  // bool(false) 

Coercive and Strict Typing with Declarations

As of PHP 7, you can enforce strict type declarations to avoid unexpected casting:

declare(strict_types=1);

function add(int $a, int $b): int {
 return $a + $b;
}

var_dump(add(2, '3'));  // TypeError

Real World Example: User Authentication

Comparison operators become really powerful in contexts like user authentication. Here’s a basic example:

function authenticateUser($username, $password) {
  // User retrieval logic...
  if ($retrievedPassword === $password) {
    return true;
  }
  return false;
}

Conclusion

In conclusion, PHP’s variety of comparison operators, from basic to complex, offers powerful tools for accurate value assessments within your applications. Mastering their correct usage is crucial for writing robust PHP code.