Control Flow 🔀

<?php
// if / elseif / else — PHP runs the FIRST block whose condition is true,
// then skips the rest. Conditions use comparison operators like >= and == .

$score = 78;
echo "Student score: $score\n";

if ($score >= 90) {
    echo "Grade: A\n";           // skipped: 78 is not >= 90
} elseif ($score >= 80) {
    echo "Grade: B\n";           // skipped: 78 is not >= 80
} elseif ($score >= 70) {
    echo "Grade: C\n";           // ✅ true! 78 >= 70 — this runs, rest skipped
} else {
    echo "Grade: F\n";           // the catch-all when nothing above matched
}

// Combine conditions with && (AND) and || (OR).
$isWeekend = true;
$temperature = 28;

if ($isWeekend && $temperature > 25) {   // BOTH must be true
    echo "Beach day!\n";
} elseif ($isWeekend || $temperature > 30) {  // EITHER is enough
    echo "Day off, but cool\n";
} else {
    echo "A normal day\n";
}
?>

Student score: 78
Grade: C
Beach day!

<?php
// switch — compare ONE value against many fixed options.
// Each 'case' is a possible value; 'break' stops PHP falling into the next case.

$day = 3;  // 1 = Monday ... 7 = Sunday
echo "Day number: $day\n";

switch ($day) {
    case 1:
        echo "Monday\n";
        break;                 // stop here — don't run case 2
    case 6:
    case 7:                    // stacked cases: 6 OR 7 run the same block
        echo "Weekend!\n";
        break;
    default:                   // runs when no case matched (here: 2,3,4,5)
        echo "A weekday\n";   // ✅ $day is 3, so this runs
        // no break needed on the LAST case, but it's tidy to add one
}
?>

Day number: 3
A weekday

<?php
// match (PHP 8) — like switch, but it RETURNS a value and uses strict
// comparison (===), so 200 only matches the integer 200, never "200".
// No 'break' needed, and commas separate the arms.

$httpCode = 404;

$message = match ($httpCode) {
    200, 201 => "Success",          // one arm can list several values
    301, 302 => "Redirect",
    404      => "Not Found",        // ✅ matches — this value is returned
    500      => "Server Error",
    default  => "Unknown",          // used if nothing else matched
};

echo "HTTP $httpCode: $message\n";   // the returned value lands in $message
?>

HTTP 404: Not Found

<?php
// Ternary  condition ? valueIfTrue : valueIfFalse  — a one-line if/else
// that produces a VALUE. Great for picking between two options.

$age = 20;
$status = ($age >= 18) ? "Adult" : "Minor";   // 20 >= 18 → "Adult"
echo "Status: $status\n";

// ?? is the 'null coalescing' operator: "use the left value, OR this
// fallback if the left is null / not set". Handy for safe defaults.
$username = null;
$display = $username ?? "Guest";              // $username is null → "Guest"
echo "Welcome, $display\n";
?>

Status: Adult
Welcome, Guest

<?php
// Alternative syntax: swap the { } braces for a colon and an 'end...' keyword.
// It reads cleanly when you weave PHP through HTML in a template.
$loggedIn = true;
?>
<?php if ($loggedIn): ?>
    <p>Welcome back!</p>
<?php else: ?>
    <p>Please log in.</p>
<?php endif; ?>

    <p>Welcome back!</p>

<?php
// 🎯 YOUR TURN — finish the if/elseif/else, then run it.
// Pick the band the temperature falls into.

$temp = 30;

if ($temp >= 30) {
    echo ___;                  // 👉  "Hot\n"
} elseif (___) {               // 👉 condition for 20 or above:  $temp >= 20
    echo "Warm\n";
} else {
    echo "Cool\n";
}

// ✅ Expected output (with $temp = 30):
//    Hot
?>

Hot

<?php
// 🎯 YOUR TURN — complete this match so it returns the right label.
// Remember: match uses  value => result  arms and needs a default.

$grade = "B";

$label = match ($grade) {
    "A" => "Excellent",
    "B" => ___,                // 👉  "Good"
    "C" => "Okay",
    ___ => "Unknown grade",    // 👉 the catch-all keyword:  default
};

echo "Grade $grade: $label\n";

// ✅ Expected output:
//    Grade B: Good
?>

Grade B: Good