Operators and Expressions

<?php

declare(strict_types=1);

$copies = $available = 3;                     // assignment is an expression with a value
$label = $copies > 0 ? 'in stock' : 'lent out';

// Since 8.0, throw is an expression: usable after ??, ?: and in arrow functions.
$isbn = $_GET['isbn'] ?? '978-0-00-000001-1';
$title = ['978-0-00-000001-1' => 'Kindred'][$isbn] ?? throw new InvalidArgumentException("Unknown ISBN {$isbn}");

echo "{$title}: {$label} ({$available})\n";   // Kindred: in stock (3)

<?php

declare(strict_types=1);

var_dump('a' . 1 + 2);          // string(2) "a3" -- (1 + 2) first since PHP 8.0
var_dump(-2 ** 2);              // int(-4)       -- ** binds tighter than unary minus

$ok = false or true;            // ($ok = false) or true
var_dump($ok);                  // bool(false)
$ok = false || true;
var_dump($ok);                  // bool(true)

<?php

declare(strict_types=1);

var_dump(2 ** 10, 2 ** -1);          // int(1024) float(0.5)
var_dump(7 % 3, -7 % 3);             // int(1) int(-1) -- sign of the dividend
var_dump(fmod(7.5, 2));              // float(1.5) -- % would truncate 7.5 to 7 (and warn)
var_dump(intdiv(-7, 2));             // int(-3)
var_dump(fdiv(1, 0));                // float(INF)

try {
    $perShelf = 120 % 0;
} catch (DivisionByZeroError $e) {
    echo get_class($e), ': ', $e->getMessage(), "\n";   // DivisionByZeroError: Modulo by zero
}

<?php

declare(strict_types=1);

$loans = 5;
echo $loans++, ' ', $loans, ' ', ++$loans, "\n";      // 5 6 7

// Shelf codes such as "Az" -> "Ba": use the explicit functions (8.3).
var_dump(str_increment('Az'), str_decrement('Ba'));  // string(2) "Ba" string(2) "Az"

$code = 'a9';
$code++;              // Deprecated (8.5): Increment on non-numeric string is deprecated, use str_increment() instead
var_dump($code);      // string(2) "b0"

<?php

declare(strict_types=1);

$report = 'Loans';
$report .= ': ';
$count = 10;
$count -= 3;
$count **= 2;
echo $report, $count, "\n";                  // Loans: 49

$options = ['format' => 'ebook'];
$options['format'] ??= 'paperback';          // kept: already set
$options['language'] ??= 'en';               // added
print_r($options);

// Array destructuring is also an assignment
[$first, , $third] = ['Solaris', 'Kindred', 'Dawn'];
echo "{$first} / {$third}\n";                // Solaris / Dawn

<?php

declare(strict_types=1);

const CAN_BORROW  = 0b001;
const CAN_RESERVE = 0b010;
const IS_STAFF    = 0b100;

$member = CAN_BORROW | CAN_RESERVE;          // set two flags
var_dump(($member & CAN_RESERVE) !== 0);     // bool(true)  test a flag
$member &= ~CAN_RESERVE;                     // clear a flag
$member ^= IS_STAFF;                         // toggle a flag
printf("%03b\n", $member);                   // 101

var_dump(1 << 3, -16 >> 2);                  // int(8) int(-4) -- arithmetic shift

echo json_encode(['title' => 'Łódź'], JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE), "\n";

<?php

declare(strict_types=1);

var_dump(1979 === 1979, '1979' === 1979, '1979' == 1979);   // bool(true) bool(false) bool(true)
var_dump('Kindred' <=> 'Dawn');                              // int(1)

<?php

declare(strict_types=1);

$handle = @fopen('/nonexistent/catalogue.csv', 'r');   // warning suppressed...
if ($handle === false) {
    $error = error_get_last();                          // ...but still retrievable
    echo 'Could not open the catalogue: ', $error['message'] ?? 'unknown error', "\n";
}

<?php

declare(strict_types=1);

// Deprecated (8.5): $files = `ls -1`;

$isbn = '978-0-00-000001-1';
// If a shell is unavoidable, escape every argument:
$output = shell_exec('echo ' . escapeshellarg($isbn));
echo $output;                                            // 978-0-00-000001-1

// Better: no shell at all (proc_open() accepts an array command since 7.4)
$process = proc_open(['echo', $isbn], [1 => ['pipe', 'w']], $pipes);
echo stream_get_contents($pipes[1]);
proc_close($process);

<?php

declare(strict_types=1);

$member = ['active' => true, 'fines' => 0];
$canBorrow = $member['active'] && $member['fines'] === 0;
var_dump($canBorrow);            // bool(true)
var_dump('Kindred' || false);    // bool(true) -- not the string
var_dump(true xor true);         // bool(false)

<?php

declare(strict_types=1);

$title = 'Kindred';
$line = 'Title: ' . $title;
$line .= ' (1979)';
echo $line, "\n";                    // Title: Kindred (1979)
echo 'Copies: ' . 2 + 1, "\n";       // Copies: 3 -- + binds tighter than . since 8.0

<?php

declare(strict_types=1);

$defaults = ['format' => 'paperback', 'language' => 'en'];
$request  = ['language' => 'es'];

print_r($request + $defaults);       // language => es, format => paperback: request wins
print_r([1, 2] + [3, 4, 5]);         // [1, 2, 5] -- union by key, not append
print_r([...[1, 2], ...[3, 4, 5]]);  // [1, 2, 3, 4, 5]

<?php

declare(strict_types=1);

interface Lendable {}
final class Book implements Lendable {}

$item = new Book();
$type = 'Lendable';

var_dump($item instanceof Book, $item instanceof Lendable, $item instanceof $type);   // all bool(true)
var_dump('Book' instanceof Book);           // bool(false): a string is not an object
var_dump($item instanceof Countable);       // bool(false)

<?php

declare(strict_types=1);

$rawTitles = "  the dispossessed\nKINDRED \n solaris  \n\n";

// Without the pipe: read from the inside out.
$titles = array_values(array_filter(array_map(trim(...), explode("\n", $rawTitles))));

// With the pipe (8.5): read from top to bottom.
$titles = $rawTitles
    |> (fn (string $s): array => explode("\n", $s))
    |> (fn (array $lines): array => array_map(trim(...), $lines))
    |> array_filter(...)
    |> array_values(...)
    |> (fn (array $t): array => array_map(ucwords(...), array_map(strtolower(...), $t)));

print_r($titles);

// Works with any single-argument callable, including invokable objects
final class Slug { public function __invoke(string $s): string { return strtolower(str_replace(' ', '-', $s)); } }
echo 'The Left Hand of Darkness' |> new Slug() |> strrev(...), "\n";

Array
(
    [0] => The Dispossessed
    [1] => Kindred
    [2] => Solaris
)
ssenkrad-fo-dnah-tfel-eht

<?php

declare(strict_types=1);

final class Author { public function __construct(public ?string $country = null) {} }
final class Book
{
    public function __construct(public string $title, public ?Author $author = null) {}
    public function author(): ?Author { return $this->author; }
}

$books = [new Book('Solaris', new Author('PL')), new Book('Anonymous pamphlet')];

foreach ($books as $book) {
    echo $book->title, ': ', $book->author()?->country ?? 'unknown', "\n";
}
// Solaris: PL
// Anonymous pamphlet: unknown