Základy jazyka PHP

/**
 Tenhle kousek kodu vypise Hello World
 a my k tomu mame viceradkovy komentar!
*/
echo "Hello World"; // JEDNORADKOVY KOMENTAR

/**
 * Specialni komentar napr. pro PHPDocumentor (~javadoc)
 * @var string $hello
 */
$hello = 'world';

$jmeno = 'promenna';
$$jmeno = 'hodnota';

echo "Promenna pojmenovana: $jmeno
obsahuje hodnotu: ${$jmeno}";

$a = 5; $b = &$a;
$b = 1; echo $a;

echo "Zpracovano " . count($rows) . " radek\n";

@mkdir("data/$user", 0755);

"ahoj" <=> "svete"  // -1
5 <=> 3             // 1
"7" <=> 7           // 0

null ?: 'fail'   // fail
5 ?: 2           // 5

$imageData = json_decode($content, true);
$width = $imageData['width'] ?? 100;

if ($a > $b)
    echo "a is bigger than b";
elseif ($a == $b) {
    echo "a is equal to b";
}
else
    echo "a is smaller than b";

switch ($i) {
    case 0:
        echo "i equals 0";
        break;
    case 1:
        echo "i equals 1";
        break;
    case 2:
        echo "i equals 2";
        break;
}

echo match ($i) {
    0 => "i equals 0",
    1 => "i equals 1",
    2 => "i equals 2"
};

$i = 10;
while ($i < 10) {
    echo $i++;
}

$i = 10;
do {
    echo $i++;
} while ($i < 10);

for ($i = 1; $i <= 10; $i++) {
    echo $i;
}

$arr = array (
  'k1' => 1, 'k2' => 2, 'k3' => 3);
foreach ($arr as $key => $value)
  echo "$key: $value";

$arr = array(1, 2, 3, 4);
foreach ($arr as &$value)
    $value = $value * 2;

print_r($arr);

function foo($arg_1, $arg_2, /* ..., */ $arg_n)
{
    echo "Example function.\n";
    return $retval;
}

foo(1, 2, ..., n);

function sum(...$numbers) {
    // $numbers je pole předaných argumentů
    $acc = 0;
    foreach ($numbers as $n) {
        $acc += $n;
    }
    return $acc;
}

echo sum(1, 2, 3, 4);

function p($n, $e = 2)
{
    return $n ** $e;
}

echo p(4);
echo p(3,3);