PHP If Statements

Conditional statements allow your program to make decisions based on conditions. The if statement is the most fundamental control structure in PHP, letting you execute code only when specific conditions are met.

Basic If Statement

The simplest form executes code when a condition is true:

<?php
if (condition) {
    // Code executes if condition is true
}
?>

Click Run to execute your code

If-Else Statement

Use else to execute alternative code when the condition is false:

<?php
$age = 16;

if ($age >= 18) {
    echo "You can vote!";
} else {
    echo "You're too young to vote.";
}
// Output: You're too young to vote.
?>

If-Elseif-Else Statement

Check multiple conditions in sequence using elseif:

<?php
$score = 85;

if ($score >= 90) {
    $grade = 'A';
} elseif ($score >= 80) {
    $grade = 'B';
} elseif ($score >= 70) {
    $grade = 'C';
} elseif ($score >= 60) {
    $grade = 'D';
} else {
    $grade = 'F';
}

echo "Grade: $grade";  // Output: Grade: B
?>

Multiple Conditions

Combine conditions using logical operators:

<?php
$age = 25;
$hasLicense = true;
$hasCar = false;

// AND: both must be true
if ($age >= 18 && $hasLicense) {
    echo "You can drive legally.\n";
}

// OR: at least one must be true
if ($hasCar || $hasLicense) {
    echo "You have some driving capability.\n";
}

// NOT: inverts the condition
if (!$hasCar) {
    echo "You don't own a car.\n";
}
?>

Nested If Statements

Place if statements inside other if statements for complex logic:

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

if ($isLoggedIn) {
    echo "Welcome!\n";

    if ($isAdmin) {
        echo "You have full access.\n";
    } else {
        if ($hasPermission) {
            echo "You can view this content.\n";
        } else {
            echo "Access denied.\n";
        }
    }
} else {
    echo "Please log in.\n";
}
?>

Alternative Syntax

PHP provides an alternative syntax useful when mixing PHP with HTML in templates:

<?php $userType = "premium"; ?>

<?php if ($userType === "premium"): ?>
    <div class="premium-badge">Premium Member</div>
<?php elseif ($userType === "basic"): ?>
    <div class="basic-badge">Basic Member</div>
<?php else: ?>
    <div class="guest-badge">Guest</div>
<?php endif; ?>

Click Run to execute your code

Truthy and Falsy Values

PHP automatically converts values to boolean in conditions. Understanding what's "falsy" is crucial:

<?php
$name = "";

if ($name) {
    echo "Hello, $name!";
} else {
    echo "Name is empty!";  // This executes
}

// Better: be explicit
if ($name !== "") {
    echo "Hello, $name!";
}
?>

Common Mistakes

<?php
$status = "active";

// ❌ WRONG: This assigns "inactive" to $status!
if ($status = "inactive") {
    echo "Account disabled";  // Always executes!
}

// ✅ CORRECT: Use == or ===
if ($status === "inactive") {
    echo "Account disabled";
}
?>

<?php
$loggedIn = true;

// ❌ WRONG: Only first line is conditional!
if ($loggedIn)
    echo "Welcome!\n";
    echo "Dashboard loaded\n";  // Always executes!

// ✅ CORRECT: Use braces
if ($loggedIn) {
    echo "Welcome!\n";
    echo "Dashboard loaded\n";
}
?>

<?php
$role = "moderator";

// ❌ Incomplete: What about other roles?
if ($role === "admin") {
    echo "Full access";
} elseif ($role === "user") {
    echo "Limited access";
}
// "moderator" gets nothing!

// ✅ CORRECT: Handle all cases
if ($role === "admin") {
    echo "Full access";
} elseif ($role === "user") {
    echo "Limited access";
} else {
    echo "Unknown role: $role";
}
?>

Exercise: User Access Control

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

if (!$isLoggedIn) {
    echo "Please log in to continue.\n";
} else {
    echo "Welcome! You are logged in.\n";

    if ($userRole === "admin") {
        echo "Permissions: Create, Read, Update, Delete, Manage Users\n";
    } elseif ($userRole === "editor") {
        echo "Permissions: Create, Read, Update\n";
    } elseif ($userRole === "viewer") {
        echo "Permissions: Read only\n";
    } else {
        echo "Unknown role. Please contact support.\n";
    }
}
?>

Summary

What's Next?

Now that you understand if statements, let's explore Switch Statements - a cleaner way to handle multiple conditions when comparing a single value against many options!