Operators

Introduction

Operators are the symbols PHP uses to perform actions on values — adding numbers, comparing them, combining strings, or checking logical conditions. You already saw a few in the last lesson while exploring type casting; this lesson covers the full set you will use in almost every PHP script you write.

Arithmetic Operators

PHP supports the standard set of arithmetic operators, plus a dedicated exponentiation operator and a modulus (remainder) operator.

<?php
    $a = 10;
    $b = 3;

    echo $a + $b;  // 13
    echo "\n";
    echo $a - $b;  // 7
    echo "\n";
    echo $a * $b;  // 30
    echo "\n";
    echo $a / $b;  // 3.3333333333333
    echo "\n";
    echo $a % $b;  // 1
    echo "\n";
    echo $a ** $b; // 1000
?>

Assignment Operators

The basic assignment operator = stores a value in a variable. PHP also offers compound assignment operators that combine an arithmetic operation with assignment in a single step.

<?php
    $score = 10;
    $score += 5;  // $score is now 15
    $score -= 2;  // $score is now 13
    $score *= 2;  // $score is now 26

    echo $score;
?>

Comparison Operators

Comparison operators check the relationship between two values and always produce a boolean result — true or false.

== vs === (Loose vs Strict)

This is one of the most important distinctions in all of PHP. The == operator ("loose equality") converts both sides to a common type before comparing, which can lead to surprising results. The === operator ("strict equality") requires both the value and the type to match exactly, with no conversion at all.

<?php
    var_dump(0 == "abc");     // In PHP 8+: false (fixed from older PHP versions)
    var_dump(0 == "");        // false
    var_dump("1" == "01");    // true - both convert to the number 1
    var_dump("10" == "1e1");  // true - both convert to the number 10
    var_dump(100 == "1e2");   // true - both convert to the number 100
    var_dump(0 == "0");       // true - both convert to the number 0

    var_dump("1" === "01");   // false - different strings, no conversion
    var_dump(100 === "1e2");  // false - int vs string, no conversion
    var_dump(0 === "0");      // false - int vs string
    var_dump(1 === 1.0);      // false - int vs float, different types
?>

The Spaceship Operator

The spaceship operator <=> compares two values and returns -1, 0, or 1 depending on whether the left side is less than, equal to, or greater than the right side. It is especially useful inside custom sorting functions.

<?php
    echo 1 <=> 2;  // -1 (1 is less than 2)
    echo "\n";
    echo 2 <=> 2;  // 0 (equal)
    echo "\n";
    echo 3 <=> 2;  // 1 (3 is greater than 2)

    // A common use case: sorting an array of numbers
    $numbers = [5, 3, 8, 1];
    usort($numbers, fn($a, $b) => $a <=> $b);
    print_r($numbers);
?>

Logical Operators

Logical operators combine or invert boolean expressions. PHP offers both symbol-based operators and word-based equivalents, which have subtly different precedence but behave the same in most everyday code.

<?php
    $isLoggedIn = true;
    $isAdmin = false;

    var_dump($isLoggedIn && $isAdmin); // false - both must be true
    var_dump($isLoggedIn || $isAdmin); // true - at least one is true
    var_dump(!$isLoggedIn);             // false - inverts true
    var_dump($isLoggedIn xor $isAdmin); // true - exactly one is true
?>

String Concatenation Operators

PHP uses the dot (.) operator to join strings together, and the .= operator to append a string onto an existing variable — the string equivalent of +=.

<?php
    $first = "Hello";
    $last = "World";

    $greeting = $first . ", " . $last . "!";
    echo $greeting; // "Hello, World!"
    echo "\n";

    $message = "Loading";
    $message .= "...";
    $message .= " done";
    echo $message; // "Loading... done"
?>

Operator Precedence

When an expression mixes multiple operators, PHP evaluates them in a fixed order of precedence — similar to the order of operations in math class. Parentheses always override the default order, so use them freely to make your intent explicit.

<?php
    echo 2 + 3 * 4;    // 14 - multiplication happens before addition
    echo "\n";
    echo (2 + 3) * 4;  // 20 - parentheses force addition first
?>

Common Mistakes

Best Practices

Frequently Asked Questions

Key Takeaways

Summary

Operators are the building blocks of every expression you will write in PHP. Of everything covered here, the == vs === distinction is the one worth committing to memory first, since it quietly causes more bugs than almost anything else in beginner PHP code.