Conditional logic is one of the most important concepts in PHP. It allows you to control the flow of your program based on different conditions. Whether you’re building a login system, form validation, or dynamic web pages, conditional statements are the foundation.

🎯 In this guide, you’ll learn:

✅ How PHP conditional statements work
✅ Using if, else, and elseif to control flow
✅ Using the switch statement for multiple cases
✅ Ternary and Null Coalescing operators for cleaner code
✅ Best practices for writing readable conditional logic

By the end, you’ll be able to write efficient conditional logic in PHP like a pro! 🚀

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1️⃣ What is Conditional Logic?

💡 Conditional logic allows your PHP program to execute different code depending on specific conditions.

Real-World Examples of Conditionals

✅ Login System: "If the password is correct, log in the user."
✅ E-commerce Checkout: "If cart total is greater than $100, apply a discount."
✅ User Access Control: "If user is an admin, show admin dashboard."

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2️⃣ The if Statement (Basic Conditional)

The if statement runs a block of code only if a condition is true.

Syntax:

if (condition) {
    // Code to execute if condition is true
}

Example: Checking Age for Voting

<?php
$age = 18;

if ($age >= 18) {
    echo "You are eligible to vote.";
}
?>

💡 Output:

You are eligible to vote.

🔥 How it works?
✅ If $age >= 18, the code inside the if block runs.

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3️⃣ The if-else Statement (Two-way Decision)

💡 The if-else statement allows you to handle both true and false cases.

Example: Checking Login Status

<?php
$isLoggedIn = false;

if ($isLoggedIn) {
    echo "Welcome, user!";
} else {
    echo "Please log in to continue.";
}
?>

💡 Output:

Please log in to continue.

🔥 How it works?
✅ If $isLoggedIn is true, the first block runs.
✅ If false, the else block runs instead.

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4️⃣ The if-elseif-else Statement (Multiple Conditions)

💡 elseif lets you check multiple conditions in a sequence.

Example: Grading System

<?php
$score = 85;

if ($score >= 90) {
    echo "Grade: A";
} elseif ($score >= 80) {
    echo "Grade: B";
} elseif ($score >= 70) {
    echo "Grade: C";
} else {
    echo "Grade: F";
}
?>

💡 Output:

Grade: B

🔥 How it works?
✅ Checks each condition in order until it finds one that’s true.
✅ If no condition is met, it falls to the else block.

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5️⃣ The switch Statement (Better for Multiple Choices)

💡 switch is great when checking multiple possible values of a variable.

Syntax:

switch (variable) {
    case value1:
        // Code to execute
        break;
    case value2:
        // Code to execute
        break;
    default:
        // Code to execute if no match is found
}

Example: Choosing a Subscription Plan

<?php
$plan = "pro";

switch ($plan) {
    case "free":
        echo "You have limited access.";
        break;
    case "pro":
        echo "You have full access!";
        break;
    case "enterprise":
        echo "You have premium features!";
        break;
    default:
        echo "Invalid plan selected.";
}
?>

💡 Output:

You have full access!

🔥 Why use switch instead of multiple if-else?
✅ More readable for multiple cases
✅ Faster execution in some cases

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6️⃣ Ternary Operator (Shorter if-else)

💡 The ternary operator is a shorthand for if-else.

Syntax:

(condition) ? "True case" : "False case";

Example: Checking Login Status

<?php
$isLoggedIn = true;
$message = $isLoggedIn ? "Welcome, user!" : "Please log in.";
echo $message;
?>

💡 Output:

Welcome, user!

🔥 Why use ternary?
✅ Shorter code
✅ Great for simple conditions

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7️⃣ Null Coalescing Operator (??)

💡 The null coalescing operator (??) checks if a variable exists, otherwise it provides a default value.

Example: Checking User Input

<?php
$username = $_GET["user"] ?? "Guest";
echo "Hello, " . $username;
?>

💡 URL:

http://example.com/?user=ZeroDev

💡 Output:

Hello, ZeroDev

🔥 If no user is provided in the URL, it defaults to "Guest"!

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8️⃣ Combining Conditions with && (AND) and || (OR)

You can check multiple conditions at once using AND (&&) and OR (||).

Example: Checking User Access

<?php
$role = "admin";
$isVerified = true;

if ($role == "admin" && $isVerified) {
    echo "Access granted!";
} else {
    echo "Access denied.";
}
?>

💡 Output:

Access granted!

🔥 Explanation:
✅ && requires both conditions to be true
✅ || requires at least one condition to be true

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9️⃣ Best Practices for Writing Conditionals

✅ Keep conditions simple and readable
❌ Bad:

if (($age > 18 && $isMember) || (!$isGuest && $plan == "premium")) { ... }

✅ Good:

$isEligible = ($age > 18 && $isMember) || (!$isGuest && $plan == "premium");
if ($isEligible) { ... }

✅ Use switch when checking multiple values of the same variable
✅ Use ternary for short if-else statements
✅ Avoid deep nesting (if inside if)

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🚀 Final Thoughts

Now you can control the flow of your PHP programs like a pro!
✅ Use if-else for basic conditions
✅ Use switch for multiple cases
✅ Use ternary (? :) for short conditions
✅ Use ?? to handle missing values
✅ Use && (AND) and || (OR) for complex conditions

👉 Next: Mastering PHP Loops

Happy coding! 🎉🚀