Conditional Statements

Conditional statements let your code make decisions: run a block when a condition is true, choose between multiple branches, and map values to results. We’ll cover if/elseif/else, switch, and modern match in depth.

Truthiness Refresher

1) if / elseif / else

<?php
  $score = 78;

  if ($score >= 90) {
    echo "Grade A";
  } elseif ($score >= 75) {
    echo "Grade B";
  } else {
    echo "Keep improving!";
  }
?>

Guard Clauses (early returns)

Instead of deep nesting, exit early when a condition fails.

<?php
  function divide($a, $b) {
    if ($b === 0) {
      return "Cannot divide by zero";
    }
    return $a / $b;
  }
?>

Short-circuit patterns

<?php
  // Execute only if condition is true
  $isAdmin = true;
  $isAdmin && print("Welcome, admin\n");

  // Provide default if empty (Elvis), or if null (??)
  $username = "";
  $label = $username ?: "Guest";
  $safe   = $_GET['name'] ?? "Guest";
?>

Alternative syntax (great for templates)

Use colon blocks in views (no braces). Close with endif;, endforeach;, etc.

<?php $loggedIn = true; ?>
<ul>
<?php if ($loggedIn): ?>
  <li>Dashboard</li>
<?php else: ?>
  <li>Login</li>
<?php endif; ?>
</ul>

2) switch

switch compares loosely by default (like ==), and falls through unless you use break.

<?php
  $role = "editor";

  switch ($role) {
    case "admin":
      echo "Full access";
      break;

    case "editor":
    case "author":
      echo "Can edit content";
      break;

    default:
      echo "Read-only";
  }
?>

switch pitfalls

• Loose comparison can surprise: switch("0") may match case 0.
• For strictly-typed checks, prefer match (PHP 8+).
• Don’t forget break (unless you want fallthrough intentionally).

3) match (PHP 8+)

match evaluates to a value, uses strict comparison (like ===), no fallthrough, and requires handling all possibilities (or a default). Excellent for mapping.

<?php
  $status = 200;

  $message = match ($status) {
    200 => "OK",
    404 => "Not Found",
    500 => "Server Error",
    default => "Unknown",
  };

  echo $message;
?>

match with conditions (boolean arms)

You can pre-compute a category and match that, or match on true and use boolean expressions in arms:

<?php
  $score = 88;

  $grade = match (true) {
    $score >= 90 => "A",
    $score >= 75 => "B",
    $score >= 60 => "C",
    default          => "D",
  };
  echo $grade;
?>

Returning values & throwing in match

<?php
  $ext = "jpg";
  $mime = match ($ext) {
    "jpg", "jpeg" => "image/jpeg",
    "png"          => "image/png",
    default         => throw new InvalidArgumentException("Unsupported ext"),
  };
?>

Common Gotchas

Real-World Examples

Role-based UI

<?php
  $role = $_GET['role'] ?? 'guest';

  $menu = match ($role) {
    'admin'  => ['Dashboard','Users','Settings'],
    'editor' => ['Dashboard','Posts'],
    default    => ['Home','Login'],
  };

  foreach ($menu as $item) {
    echo "$item\n";
  }
?>

Validation flow (guard + detailed reasons)

<?php
  function validateAge($age) {
    if (!is_numeric($age)) {
      return "Age must be numeric";
    }
    if ($age < 0) {
      return "Age cannot be negative";
    }
    return "OK";
  }
?>

Practice Tasks

1. Read $_GET['lang'] and use match to print a greeting for en, hi, es, with default fallback.
2. Write a function grade($score) using match(true) that returns A/B/C/D.
3. Refactor a nested if that checks multiple invalid states into clear guard-clauses.
4. Demonstrate a switch with intentional fallthrough for related categories.
5. Show the difference between $x = true or false and $x = true || false (precedence!).