<?php

// -----------------------------
// IF statement
// -----------------------------

if ($condition) {
  // code.
}

// E.g.
if ($year === 2024) {
  $isOlympicYear = TRUE;
}

// Bonus: IF statements with a lot of conditions
if (
  $condition_1 &&
  (
    $condition_2 ||
    $condition_3
  ) &&
  $condition_4
) {
  // code.
}

// -----------------------------
// IF/ELSE statement
// -----------------------------

if ($condition) {
  // code.
}
else {
  // other code.
}

// E.g.
if ($year === 2024) {
  $isOlympicYear = TRUE;
}
else {
  $isOlympicYear = FALSE;
}

// Alternatively, you could write the above like this.
$isOlympicYear = FALSE;
if ($year === 2024) {
  $isOlympicYear = TRUE;
}

// -----------------------------
// ELSEIF statements.
// -----------------------------

if ($condition_1) {
  // code.
}
elseif ($condition_2) {
  // other code.
}
else {
  // other other code.
}

// E.g. 
if ($year === 2024) {
  $isOlympicYear = TRUE;
}
elseif ($year === 2025) {
  $isOlympicYear = FALSE;
}

// -----------------------------
// Nesting statements
// -----------------------------

// E.g.
if ($year === 2024) {
  $isOlympicYear = TRUE;

  if ($city === 'Paris') {
    echo "Bonjour!";
  }
  else {
    echo "Hello!";
  }
}

// -----------------------------
// Early Return statements
// -----------------------------

function checkAge($age) {
  // Early return if age is less than 18
  if ($age < 18) {
    return "Too young";
  }
  // Continue with the function if age is 18+
  return "Welcome!";
}

echo checkAge(16); // Outputs: Too young
echo checkAge(20); // Outputs: Welcome!
  
// -----------------------------
// Ternary Expressions
// - Only good for replacing non-complex IF/ELSE statements
// -----------------------------

$age = 20;
$can_vote = ($age >= 18) ? 'Yes' : 'No'

// Alternatively, you could write the above like this, but the above saves lines of code.
if ($age >= 18) {
  $can_vote = 'Yes';
}
else {
  $can_vote = 'No';
}

// -----------------------------
// Switch statements
// -----------------------------

// E.g.
switch ($isOlympicYear) {
  case 2023:
    break; // Without a break, the code will continue executing to the next case.

  case 2024:
    break;

  case 2025:
    break;

  default: // Default is the equivalent to an ELSE
    break;
}

// Using a switch like above instead of the following
if ($year === 2023) {
  //
}
elseif ($year === 2024) {
  //
}
elseif ($year === 2025) {
  //
}

// -----------------------------
// For loops
// -----------------------------

// E.g.
for ($i = 1; $i < 5; $i++) {
  echo "This is the $i -th iteration.";
}

// -----------------------------
// While loops
// -----------------------------

// E.g.
$i = 1;
while ($i < 5) {
  echo "This is the $i -th iteration.";
  $i++;
}

// -----------------------------
// Passing Arguments by Reference
// -----------------------------

function add_five(&$value) {
  $value += 5;
}

$num = 2;
add_five($num);
echo $num; // Outputs: 7

// -----------------------------
// Using the ... operator
// - Allows for any number of arguments 
// -----------------------------

function sum(...$numbers) {
  $sum = 0;
  
  for ($i = 0; $i < count($numbers); $i++) {
    $sum += $numbers[$i];
  }

  return $sum;
}

echo sum(1, 2, 3, 4); // Output: 10