Conditional Statements

Introduction

Almost every useful program needs to make decisions: show a discount if the cart total is over a certain amount, greet a user differently depending on the time of day, or reject a form if a required field is empty. PHP gives you several tools for this, and choosing the right one makes your code easier to read.

In this lesson you will learn the classic if/elseif/else chain, nested conditionals, the compact ternary operator, the null coalescing operator for safe fallback values, and the switch statement — plus a preview of the cleaner match expression PHP 8 introduced, which the next lesson covers in depth.

The if Statement

The if statement runs a block of code only when its condition evaluates to true. The condition is any expression that produces a boolean value.

<?php
$age = 20;

if ($age >= 18) {
    echo "You are an adult.";
}

You are an adult.

If the condition is false, the block inside the braces is simply skipped, and execution continues after it.

if / elseif / else

To handle more than two outcomes, chain elseif blocks between if and a final else. PHP checks each condition in order and runs the first block whose condition is true; else only runs if none of them matched.

<?php
$score = 72;

if ($score >= 90) {
    echo "Grade: A";
} elseif ($score >= 75) {
    echo "Grade: B";
} elseif ($score >= 60) {
    echo "Grade: C";
} else {
    echo "Grade: F";
}

Grade: C

Nested Conditionals

An if statement can contain another if statement inside it. This is useful when a second decision only makes sense after the first condition is already true.

<?php
$isLoggedIn = true;
$role = "editor";

if ($isLoggedIn) {
    if ($role === "admin") {
        echo "Welcome, Admin!";
    } else {
        echo "Welcome, valued user!";
    }
} else {
    echo "Please log in.";
}

Welcome, valued user!

Nesting works well for a level or two, but deeply nested conditionals become hard to read. Combining conditions with && or restructuring the logic often produces cleaner code than nesting five levels deep.

The Ternary Operator

The ternary operator lets you write a simple if/else as a single expression: condition ? valueIfTrue : valueIfFalse. It is most useful for short assignments, not complex branching logic.

<?php
$age = 16;

$status = ($age >= 18) ? "adult" : "minor";
echo "Status: $status";

Status: minor

PHP also supports a shorthand ternary, ?:, which returns the left-hand value if it is truthy, or the right-hand value otherwise.

<?php
$nickname = "";

$displayName = $nickname ?: "Guest";
echo $displayName;

Guest

The Null Coalescing Operator

The null coalescing operator, ??, returns its left-hand operand if it exists and is not null; otherwise it returns the right-hand operand. Unlike ?:, it does not trigger a warning when the variable is undefined, which makes it perfect for safe fallback values — especially with array keys or form input that might not be set.

<?php
$settings = [
    "theme" => "dark",
];

$theme = $settings["theme"] ?? "light";
$fontSize = $settings["fontSize"] ?? "16px";

echo "Theme: $theme, Font size: $fontSize";

Theme: dark, Font size: 16px

You can also chain multiple ?? operators to try several fallbacks in order, and PHP has a shorthand assignment version, ??=, that only assigns a value if the variable is currently null.

<?php
$username = null;

$username ??= "anonymous";
echo $username;

anonymous

The switch Statement

When you need to compare one value against many possible matches, switch can be clearer than a long elseif chain. Each case is checked using loose comparison (==), and execution "falls through" to the next case unless you explicitly stop it with break.

<?php
$day = "Wed";

switch ($day) {
    case "Mon":
        echo "Start of the work week";
        break;
    case "Wed":
        echo "Midweek check-in";
        break;
    case "Fri":
        echo "Almost the weekend!";
        break;
    default:
        echo "Just another day";
        break;
}

Midweek check-in

<?php
$day = "Wed";

switch ($day) {
    case "Wed":
        echo "Midweek check-in. ";
        // missing break!
    case "Fri":
        echo "Almost the weekend!";
        break;
}

Midweek check-in. Almost the weekend!

Multiple case labels can share the same block by stacking them, which is a clean way to group several values that should behave identically.

<?php
$day = "Sat";

switch ($day) {
    case "Sat":
    case "Sun":
        echo "It's the weekend!";
        break;
    default:
        echo "It's a weekday.";
        break;
}

It's the weekend!

Looking Ahead: match

PHP 8 introduced the match expression as a cleaner alternative to switch. It uses strict comparison by default, never falls through, and directly returns a value instead of requiring you to assign one manually inside each case. The next lesson covers match in detail, including a side-by-side comparison with an equivalent switch statement.

Common Mistakes

Best Practices

Frequently Asked Questions

Key Takeaways

Summary

Conditional statements are how your PHP programs make decisions. You now know how to branch with if/elseif/else, nest conditions, write compact expressions with the ternary and null coalescing operators, and compare a value against multiple cases with switch — while remembering the classic break pitfall.