PHP Conditional Statements: if, else, elseif Tutorial

Conditional statements are the foundation of programming in PHP. They allow your script to make decisions: execute one part of code or another depending on conditions. Without conditionals, it would be difficult to write user logins, shopping cart logic, form validation, or personalized content.

In this lesson, you’ll learn the basics: if, else, and elseif.
You’ll see simple and practical PHP code examples.
You’ll learn best practices and avoid common mistakes.

The previous chapter covered indexed and associative arrays and array functions like map, filter, and reduce - now we’ll show how to combine arrays with conditionals (e.g., checking if an array is not empty before doing something).

Basics of Conditional Statements in PHP

What is a condition?

A condition is an expression that evaluates to a boolean: true or false. Based on this result, PHP decides which block of code to execute.

if (condition) - executes the block if the condition is true.
else - executes the alternative block if the condition is false.
elseif (another_condition) - adds more tests if the previous ones were not met.

if syntax

<?php
$isLoggedIn = true;

if ($isLoggedIn) {
    echo "Welcome back!";
}

if...else syntax

<?php
$hour = (int) date('H'); // e.g. 0..23

if ($hour < 12) {
    echo "Good morning!";
} else {
    echo "Good evening!";
}

if...elseif...else syntax

PHP executes only the first block where the condition is true; the rest are skipped.

<?php
$points = 78;

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

Important: truthy and falsy in PHP

In PHP, some values are treated as false, even if they’re not literally false:

False: false, 0, 0.0, "" (empty string), "0" (string zero!), [] (empty array), null
True: everything else (e.g., "abc", 1, -5, [1,2], object)

⚠️ Note: "0" is treated as false - a common source of confusion.

Comparison and logical operators

Comparisons: ==, === (identical: type and value), !=, !==, <, >, <=, >=
Logical: && (and), || (or), ! (not)
There are also and, or with lower precedence - usually stick to && and ||.

If any of these look unfamiliar, the lesson on arithmetic, comparison, and logical operators walks through each of them in detail.

PHP Code Examples (with comments)

1) Simple condition: access only for adults

<?php
$age = 19;

if ($age >= 18) {
    echo "You have access to this section.";
}

2) if...else: greeting depending on the time

<?php
$hour = (int) date('H');

if ($hour < 12) {
    echo "Good morning!";
} else {
    echo "Good afternoon!";
}

3) if...elseif...else: discount thresholds

<?php
$cartValue = 260;

if ($cartValue >= 500) {
    echo "15% discount";
} elseif ($cartValue >= 200) {
    echo "7% discount";
} elseif ($cartValue >= 100) {
    echo "3% discount";
} else {
    echo "No discount";
}

4) Nested conditions and combining operators

<?php
$country = "PL";
$age = 20;
$hasConsent = true;

if ($country === "PL" && $age >= 18) {
    if ($hasConsent) {
        echo "You can participate in the contest.";
    } else {
        echo "We need your consent.";
    }
} else {
    echo "Criteria not met.";
}

5) Working with arrays (linking to previous lesson)

<?php
$products = ["monitor", "mouse", "keyboard"];

// empty($products) returns true for an empty array
if (!empty($products)) {
    echo "We have " . count($products) . " products in stock.";
} else {
    echo "No products available.";
}

// Checking for a value in an array
if (in_array("mouse", $products, true)) { // true => strict comparison
    echo "Mouse is available.";
}

6) Safe key checking in associative arrays

<?php
$user = [
    "login" => "ola",
    // "age" => 17 // commented: key may not exist
];

// isset checks if the key exists and is not null
if (isset($user["age"]) && $user["age"] >= 18) {
    echo "User is an adult.";
} else {
    echo "Age missing or user underage.";
}

7) Loose vs strict comparisons (== vs ===)

<?php
$num = 0;
$text = "0";

if ($num == $text) {
    echo "== considers values equal (type conversion).";
}

if ($num === $text) {
    echo "This won’t print, because types differ (int vs string).";
}

8) Beware operator precedence: && vs and

<?php
$result = false;
$a = true;
$b = false;

// && has higher precedence than =
$result = $a && $b; // ($a && $b) → false, then assignment
var_dump($result); // bool(false)

// and has lower precedence than =
$result = $a and $b; // ($result = $a) → true assigned, then true and $b → false
var_dump($result); // bool(true) - surprise!

// Use && and || and add parentheses for clarity

9) Using if in templates (alternative syntax)

Alternative syntax with endif; helps mixing PHP with HTML.

<?php
$isLoggedIn = true;
$login = "ola";
?>

<div class="welcome">
    <?php if ($isLoggedIn): ?>
        <p>Welcome, <?= htmlspecialchars($login) ?>!</p>
    <?php elseif (!$isLoggedIn): ?>
        <p>Welcome, Guest!</p>
    <?php else: ?>
        <p>Unknown login state.</p>
    <?php endif; ?>
</div>

Best Practices and Common Mistakes

Best Practices

Always use curly braces { }, even for single statements - improves readability and prevents errors.
Prefer strict comparisons (===, !==) instead of == and !=, especially for form/API data.

Simplify conditions - use well-named intermediate variables:

$isAdult = isset($user["age"]) && $user["age"] >= 18;
if ($isAdult) { ... }

Avoid deep nesting - use guard clauses (early returns):

if (!$isLoggedIn) {
    echo "Please log in";
    return;
}
// further code for logged-in users...

Add parentheses in complex conditions for clarity.
Stick to one convention: use elseif (recommended) instead of else if.
Use isset() to check if keys exist; use empty() for “is empty” (be careful with "0").
Escape output in HTML (e.g., htmlspecialchars) and validate inputs.

Common Mistakes

Using = instead of == or === in conditions:

if ($a = 5) { ... } // ERROR: assignment instead of comparison

Missing braces leading to “dangling else” problems.
Confusing precedence of and/or with &&/|| - stick to && and ||.
Misunderstanding truthy/falsy: e.g., "0" is false, so if ("0") { ... } won’t run.

Checking values without confirming key existence: Instead:

if ($user["age"] > 18) { ... } // Notice if 'age' doesn’t exist

if (isset($user["age"]) && $user["age"] > 18) { ... }

Comparing to null loosely (==) instead of strictly (=== or is_null()).

Summary

Conditional statements if, else, elseif control program flow in PHP.
Conditions rely on true/false; remember truthy/falsy rules.
Use strict comparisons (===, !==), braces, and parentheses for clarity and safety.
Avoid pitfalls: = instead of ==, precedence issues with and, missing isset().
Alternative syntax if: ... elseif: ... else: ... endif; is handy in templates.

Mini Quiz - Test Yourself!

What will this print?

<?php
$value = "0";
if ($value) {
    echo "A";
} else {
    echo "B";
}

➡️ B

Which syntax is recommended in PHP? ➡️ elseif
What’s the output?

var_dump(0 == "0");
var_dump(0 === "0");

➡️ true, false

Safer way to check user’s age in $u: ➡️ if (isset($u["age"]) && $u["age"] >= 18) { ... }
Difference between && and and? ➡️ Both are logical AND, but with different precedence.
What prints?

$result = false;
$a = true;
$b = false;

$result = $a and $b;
var_dump($result);

➡️ bool(true)

In an if ... elseif ... else chain, which block executes? ➡️ Only the first block where the condition is true.
True or false: empty([]) returns true. ➡️ True
What’s the result?

if ("10" > 2) {
    echo "X";
} else {
    echo "Y";
}

➡️ X

Which comparison is safer for form data (string vs int)? ➡️ ===

Now you know the basic conditional statements in PHP: if, else, and elseif. Practice creating conditions based on form data and arrays, and you’ll quickly feel confident programming in PHP. Later in this chapter you’ll add two more tools for the same job: the switch statement and the match expression.