Loops 🔁

<?php
// A FOR loop is for when you know HOW MANY times to repeat.
// It has three parts inside ( ) separated by semicolons:
//   1) start:  $i = 1        — runs once, before the loop
//   2) check:  $i <= 5       — tested before every pass; loop runs while true
//   3) step:   $i++          — runs after every pass ($i++ means "add 1 to $i")

for ($i = 1; $i <= 5; $i++) {
    echo "Count: $i\n";      // PHP swaps $i for its value inside "double quotes"
}

echo "Done!\n";              // runs once, AFTER the loop finishes
?>

Count: 1
Count: 2
Count: 3
Count: 4
Count: 5
Done!

<?php
// A WHILE loop repeats as long as a condition stays true.
// Use it when you DON'T know the count up front — here we stop when a
// total passes 100. You must change something inside the loop, or it
// would run forever.

$total = 0;       // start at zero
$day = 0;         // counts how many days we added

while ($total < 100) {        // keep going WHILE total is under 100
    $day++;                   // move to the next day (add 1)
    $total += 20;             // $total += 20  is short for  $total = $total + 20
    echo "Day $day: total is $total\n";
}

echo "Reached the goal in $day days.\n";
?>

Day 1: total is 20
Day 2: total is 40
Day 3: total is 60
Day 4: total is 80
Day 5: total is 100
Reached the goal in 5 days.

<?php
// A DO-WHILE loop runs the body FIRST, then checks the condition.
// So it always runs AT LEAST ONCE — even if the condition is false to begin
// with. Perfect for "show a menu, then ask again" style code.

$count = 10;

do {
    echo "Body ran with count = $count\n";   // this prints once...
    $count++;
} while ($count < 5);                          // ...even though 10 < 5 is false

echo "Notice the body ran once despite the false condition.\n";
?>

Body ran with count = 10
Notice the body ran once despite the false condition.

<?php
// FOREACH is PHP's most-used loop — it walks through every item in an array.
// The simplest form gives you each VALUE in turn:  foreach ($arr as $value)

$fruits = ["Apple", "Banana", "Cherry", "Date"];

foreach ($fruits as $fruit) {        // $fruit holds one item each time round
    echo "I like $fruit\n";
}

echo "That's " . count($fruits) . " fruits.\n";   // count() = how many items
?>

I like Apple
I like Banana
I like Cherry
I like Date
That's 4 fruits.

<?php
// The KEY => VALUE form gives you BOTH the key and the value each pass.
// For a list, the key is the position (0, 1, 2...).
// For an associative array (named keys), the key is the name.

$prices = ["coffee" => 3.50, "muffin" => 2.00, "juice" => 4.25];

foreach ($prices as $item => $price) {       // $item = key, $price = value
    echo "$item costs \$$price\n";          // \$ prints a literal $ sign
}

// It works on a plain list too — here the key is the index:
$colours = ["red", "green", "blue"];
foreach ($colours as $index => $colour) {
    echo "[$index] $colour\n";
}
?>

coffee costs $3.5
muffin costs $2
juice costs $4.25
[0] red
[1] green
[2] blue

<?php
// BREAK stops the loop completely. CONTINUE skips the rest of THIS pass
// and jumps to the next one. Both are usually paired with an if.

echo "=== break: stop at the first match ===\n";
$numbers = [3, 7, 12, 5, 20];
foreach ($numbers as $num) {
    if ($num > 10) {
        echo "Found one over 10: $num — stopping.\n";
        break;                      // leave the loop entirely
    }
    echo "Checked $num, too small.\n";
}

echo "\n=== continue: skip the even ones ===\n";
for ($i = 1; $i <= 6; $i++) {
    if ($i % 2 === 0) {             // % is remainder; even numbers give 0
        continue;                   // skip the echo, go to next $i
    }
    echo "Odd: $i\n";
}

// LEVELS: break 2 / continue 2 act on the OUTER loop, not just the inner one.
echo "\n=== break 2: leave BOTH loops at once ===\n";
for ($row = 1; $row <= 3; $row++) {
    for ($col = 1; $col <= 3; $col++) {
        if ($row === 2 && $col === 2) {
            echo "Hit ($row,$col) — break 2 leaves both loops.\n";
            break 2;                // not just the inner loop — both
        }
        echo "At ($row,$col)\n";
    }
}
?>

=== break: stop at the first match ===
Checked 3, too small.
Checked 7, too small.
Found one over 10: 12 — stopping.

=== continue: skip the even ones ===
Odd: 1
Odd: 3
Odd: 5

=== break 2: leave BOTH loops at once ===
At (1,1)
At (1,2)
At (1,3)
At (2,1)
Hit (2,2) — break 2 leaves both loops.

<?php
// 🎯 YOUR TURN — print a countdown from 5 down to 1, then "Lift off!".
// A countdown goes DOWNWARDS, so the step must SUBTRACT. Fill the blanks.

for ($i = 5; $i ___ 1; $i--) {     // 👉 keep going while $i is >= 1  (use:  >= )
    echo ___;                      // 👉 echo the number then a newline, e.g.  "$i\n"
}
echo "Lift off!\n";

// ✅ Expected output:
//    5
//    4
//    3
//    2
//    1
//    Lift off!
?>

5
4
3
2
1
Lift off!

<?php
// 🎯 YOUR TURN — print each student and their score using KEY => VALUE.
// Fill the two blanks so PHP gives you both the name (key) and the mark (value).

$scores = ["Maya" => 88, "Owen" => 73, "Priya" => 95];

foreach ($scores as ___ => ___) {       // 👉 first blank = the key, second = the value
    echo "$name scored $score\n";       // 👉 so name your variables  $name  and  $score
}

// ✅ Expected output:
//    Maya scored 88
//    Owen scored 73
//    Priya scored 95
?>

Maya scored 88
Owen scored 73
Priya scored 95

<?php
// ALTERNATIVE SYNTAX: instead of { } you can use a colon and an "end" word.
// This reads much better when you mix loops with HTML in a template, because
// the closing endforeach / endfor is clearer than a lonely }.

$users = ["Ada", "Linus", "Grace"];
?>
<ul>
<?php foreach ($users as $user): ?>
    <li><?php echo $user; ?></li>
<?php endforeach; ?>
</ul>

<?php for ($n = 1; $n <= 3; $n++): ?>
<p>Row <?php echo $n; ?></p>
<?php endfor; ?>

<ul>
    <li>Ada</li>
    <li>Linus</li>
    <li>Grace</li>
</ul>

<p>Row 1</p>
<p>Row 2</p>
<p>Row 3</p>

<?php
// REAL-WORLD: total up an online order, skipping out-of-stock items.
// This combines foreach (key => value), continue, and a running total —
// the exact pattern you'll use on real shopping carts.

$cart = [
    "Laptop"   => 999.00,
    "Mouse"    => 25.50,
    "Keyboard" => 0,        // 0 means out of stock — we'll skip it
    "Monitor"  => 180.75,
];

$total = 0;
$lines = 0;

foreach ($cart as $product => $price) {
    if ($price <= 0) {
        echo "$product: out of stock (skipped)\n";
        continue;                       // don't add it to the total
    }
    $total += $price;
    $lines++;
    printf("%-9s \$%.2f\n", $product, $price);   // %-9s pads the name to 9 chars
}

echo "-------------------\n";
printf("Items: %d   Total: \$%.2f\n", $lines, $total);
?>

Laptop    $999.00
Mouse     $25.50
Keyboard: out of stock (skipped)
Monitor   $180.75
-------------------
Items: 3   Total: $1205.25