PHP Control Structures and Functions¶

PHP control structures include if/elseif/else, switch, match (PHP 8), for/foreach/while. The match expression uses strict comparison and returns values - preferred over switch. Functions support type hints, default values, variadic params, named arguments (PHP 8), closures (use), and arrow functions (fn).

Key Facts¶

match (PHP 8) = strict comparison, returns value, no fallthrough (replaces switch)
foreach ($arr as $key => $value) - primary array loop
Ternary: $x ?: 'default' (falsy); null coalescing: $x ?? 'default' (null only)
Spaceship <=> returns -1, 0, 1 - used in usort
Named arguments (PHP 8): htmlspecialchars(string: $s, double_encode: false)
Arrow functions (PHP 7.4): fn($x) => $x * 2 - auto-capture, single expression

Patterns¶

Match Expression¶

$result = match($status) {
    'active', 'verified' => 'Access granted',
    'pending'            => 'Awaiting approval',
    'banned'             => 'Access denied',
    default              => 'Unknown',
};

Functions and Closures¶

// Typed function
function greet(string $name, string $greeting = "Hello"): string {
    return "$greeting, $name!";
}

// Variadic
function sum(int ...$nums): int { return array_sum($nums); }

// Closure (captures via use)
$tax = 0.2;
$calc = function(float $price) use ($tax): float {
    return $price * (1 + $tax);
};

// Arrow function (auto-captures, single expression)
$calc = fn(float $price): float => $price * (1 + $tax);

Null Handling¶

$name = $_GET['name'] ?? 'Guest';    // null coalescing
$name ??= 'Guest';                    // null coalescing assignment
$len = $user?->profile?->name;        // nullsafe operator (PHP 8)

String Functions and Dates¶

// String manipulation
strtolower($s); strtoupper($s);
trim($s); ltrim($s); rtrim($s);
str_replace('old', 'new', $s);
explode(',', $csv);   // string -> array
implode(', ', $arr);  // array -> string
substr($s, 0, 5);
sprintf("Price: $%.2f", 9.99);

// Dates
echo date('Y-m-d H:i:s');           // 2026-04-03 12:00:00
echo date('D, M jS Y', $timestamp); // Thu, Apr 3rd 2026
$dt = new DateTime('2026-01-01');
$dt->modify('+30 days');
$diff = $dt->diff(new DateTime());

Gotchas¶

switch uses loose comparison and falls through without break - prefer match
Arrow functions capture by value, not reference - mutations don't affect outer scope
foreach ($arr as &$value) - unset $value after loop to avoid last-element bugs
date() uses server timezone; date_default_timezone_set('UTC') for consistency