Conditional Statements in PHP

What Are Conditional Statements?

Conditional statements allow your PHP script to make decisions. Based on whether a condition is true or false, the program executes a block of code.

This enables dynamic behavior — for example, showing a welcome message to logged-in users, or redirecting users who haven’t completed a form.

Using if, else, and elseif

Basic if Statement:

<?php
$age = 18;

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

<?php
$age = 18;

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

if-else Statement:

<?php
$isMember = false;

if ($isMember) {
  echo "Welcome back!";
} else {
  echo "Please sign up.";
}
?>

<?php
$isMember = false;

if ($isMember) {
  echo "Welcome back!";
} else {
  echo "Please sign up.";
}
?>

if-elseif-else Statement:

<?php
$marks = 75;

if ($marks >= 90) {
  echo "Grade: A";
} elseif ($marks >= 75) {
  echo "Grade: B";
} elseif ($marks >= 50) {
  echo "Grade: C";
} else {
  echo "Grade: F";
}
?>

<?php
$marks = 75;

if ($marks >= 90) {
  echo "Grade: A";
} elseif ($marks >= 75) {
  echo "Grade: B";
} elseif ($marks >= 50) {
  echo "Grade: C";
} else {
  echo "Grade: F";
}
?>

This structure is useful when you have multiple possible outcomes.

Real-World Example: Login Status

<?php
$isLoggedIn = true;
$username = "Emma";

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

<?php
$isLoggedIn = true;
$username = "Emma";

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

This is a common pattern used on websites that manage user accounts.

Nested Conditional Statements

You can also place one condition inside another — this is called nesting.

Example:

<?php
$role = "admin";
$status = "active";

if ($role == "admin") {
  if ($status == "active") {
    echo "Access granted to admin dashboard.";
  } else {
    echo "Your account is not active.";
  }
} else {
  echo "You are not an admin.";
}
?>

<?php
$role = "admin";
$status = "active";

if ($role == "admin") {
  if ($status == "active") {
    echo "Access granted to admin dashboard.";
  } else {
    echo "Your account is not active.";
  }
} else {
  echo "You are not an admin.";
}
?>

Although nesting is powerful, it’s best used sparingly to keep code readable.

Using switch Statement in PHP

The switch statement is a cleaner way to compare a single variable against multiple values.

Syntax:

switch (variable) {
  case value1:
    // code to execute
    break;
  case value2:
    // code to execute
    break;
  default:
    // default code
}

switch (variable) {
  case value1:
    // code to execute
    break;
  case value2:
    // code to execute
    break;
  default:
    // default code
}

Example:

<?php
$day = "Saturday";

switch ($day) {
  case "Monday":
    echo "Start of work week";
    break;
  case "Saturday":
  case "Sunday":
    echo "It's weekend!";
    break;
  default:
    echo "Midweek day";
}
?>

<?php
$day = "Saturday";

switch ($day) {
  case "Monday":
    echo "Start of work week";
    break;
  case "Saturday":
  case "Sunday":
    echo "It's weekend!";
    break;
  default:
    echo "Midweek day";
}
?>

The switch block is especially useful when checking the value of enums, request types, or specific user actions.

Common Mistakes to Avoid

• Forgetting to use == or === in comparisons.
• Missing break statements in switch, which causes fall-through.
• Using assignment = instead of comparison == in if conditions.
• Writing overly nested conditions that are hard to maintain.

Best Practices

• Use strict comparison (===) where type safety matters.
• Avoid deep nesting by combining conditions logically.
• Use switch when checking against multiple fixed values.
• Keep conditionals readable with proper indentation and spacing.
• Use parentheses to clarify complex logical expressions.

Notes:

• Conditional statements let your code make decisions.
• Use if, else, and elseif for simple branching.
• Use switch when evaluating a single variable against many values.
• Avoid unnecessary nesting and write clear, readable conditions.

Practice Tasks

Task 1: Age Verifier
Create a PHP script that checks a person’s age and prints:

• Under 13: “You are a child.”
• 13–17: “You are a teenager.”
• 18+: “You are an adult.”

Task 2: Payment Status
Set a $status = "paid" variable and print:

• If “paid” → “Payment successful”
• If “pending” → “Awaiting confirmation”
• If “failed” → “Payment failed”
• Else → “Invalid status”

Task 3: Day Checker
Use switch to print messages for each day of the week.
Example: “Today is Monday. Let’s be productive!”