PHP Loops

Types of Loops

<?php
for ($i = 0; $i < 5; $i++) {
    echo $i;
}
?>

<?php
$i = 0;
while ($i < 5) {
    echo $i;
    $i++;
}
?>

<?php
$i = 0;
do {
    echo $i;
    $i++;
} while ($i < 5);
?>

<?php
$arr = [1, 2, 3];
foreach ($arr as $val) {
    echo $val;
}
?>

🔹 for Loop

Use when you know how many times to loop:

<?php
// Basic for loop
for ($i = 1; $i <= 5; $i++) {
    echo "Number: $i<br>";
}
echo "<br>";

// Counting backwards
for ($i = 5; $i >= 1; $i--) {
    echo "$i... ";
}
echo "Blast off!<br><br>";

// Increment by 2
for ($i = 0; $i <= 10; $i += 2) {
    echo "$i ";
}
echo "<br><br>";

// Multiplication table
for ($i = 1; $i <= 5; $i++) {
    echo "5 x $i = " . (5 * $i) . "<br>";
}
?>

🔹 while Loop

Loop while a condition is true:

<?php
// Basic while loop
$count = 1;
while ($count <= 5) {
    echo "Count: $count<br>";
    $count++;
}
echo "<br>";

// Sum numbers
$sum = 0;
$num = 1;
while ($num <= 10) {
    $sum += $num;
    $num++;
}
echo "Sum of 1 to 10: $sum<br><br>";

// User input simulation
$password = "secret";
$attempt = "wrong";
$tries = 0;

while ($attempt != $password && $tries < 3) {
    $tries++;
    echo "Attempt $tries: Incorrect password<br>";
    // In real scenario, get user input here
    if ($tries == 2) $attempt = "secret"; // Simulate correct on 3rd try
}
if ($attempt == $password) {
    echo "Access granted!";
}
?>

🔹 do...while Loop

Execute code at least once, then check condition:

<?php
// Basic do...while
$i = 1;
do {
    echo "Number: $i<br>";
    $i++;
} while ($i <= 5);
echo "<br>";

// Executes at least once even if condition is false
$x = 10;
do {
    echo "This runs once even though x is not less than 5<br>";
    $x++;
} while ($x < 5);
echo "<br>";

// Menu system example
$choice = 0;
$menuShown = 0;
do {
    $menuShown++;
    echo "Menu (shown $menuShown time)<br>";
    echo "1. Option One<br>";
    echo "2. Option Two<br>";
    echo "3. Exit<br><br>";
    
    // Simulate user choosing exit on 2nd show
    if ($menuShown == 2) $choice = 3;
} while ($choice != 3);
echo "Goodbye!";
?>

🔹 foreach Loop

Loop through arrays easily:

<?php
// Simple array
$colors = ["Red", "Green", "Blue", "Yellow"];
foreach ($colors as $color) {
    echo "$color<br>";
}
echo "<br>";

// Array with index
$fruits = ["Apple", "Banana", "Orange"];
foreach ($fruits as $index => $fruit) {
    echo "$index: $fruit<br>";
}
echo "<br>";

// Associative array
$person = [
    "name" => "John",
    "age" => 30,
    "city" => "New York"
];
foreach ($person as $key => $value) {
    echo "$key: $value<br>";
}
echo "<br>";

// Array of arrays
$students = [
    ["name" => "Alice", "grade" => "A"],
    ["name" => "Bob", "grade" => "B"],
    ["name" => "Charlie", "grade" => "A"]
];
foreach ($students as $student) {
    echo $student["name"] . " got grade " . $student["grade"] . "<br>";
}
?>

🔹 break and continue

Control loop execution flow:

<?php
// break - exit loop completely
echo "Using break:<br>";
for ($i = 1; $i <= 10; $i++) {
    if ($i == 5) {
        echo "Breaking at $i<br>";
        break;
    }
    echo "$i ";
}
echo "<br><br>";

// continue - skip current iteration
echo "Using continue:<br>";
for ($i = 1; $i <= 10; $i++) {
    if ($i % 2 == 0) {
        continue; // Skip even numbers
    }
    echo "$i "; // Only odd numbers printed
}
echo "<br><br>";

// Practical example
$numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
echo "Find first number greater than 5:<br>";
foreach ($numbers as $num) {
    if ($num <= 5) {
        continue;
    }
    echo "Found: $num";
    break;
}
?>

🔹 Nested Loops

Loops inside other loops:

<?php
// Multiplication table
echo "Multiplication Table:<br>";
for ($i = 1; $i <= 3; $i++) {
    for ($j = 1; $j <= 3; $j++) {
        $result = $i * $j;
        echo "$i x $j = $result<br>";
    }
    echo "<br>";
}

// Pattern printing
echo "Pattern:<br>";
for ($i = 1; $i <= 4; $i++) {
    for ($j = 1; $j <= $i; $j++) {
        echo "* ";
    }
    echo "<br>";
}
?>