Control Structures

if / elseif / else

<?php
if ($x > 0) {
    echo "positive";
} elseif ($x < 0) {
    echo "negative";
} else {
    echo "zero";
}

while

<?php
$i = 0;
while ($i < 10) {
    echo $i;
    $i++;
}

do…while

<?php
$i = 0;
do {
    $i++;
} while ($i < 10);

for

<?php
for ($i = 0; $i < 10; $i++) {
    echo $i;
}

foreach

<?php
$arr = [1, 2, 3];
foreach ($arr as $value) {
    echo $value . "\n";
}

// With key binding (indexed arrays)
foreach ($arr as $i => $value) {
    echo "$i: $value\n";
}

// With key binding (associative arrays)
$map = ["name" => "Alice", "age" => "30"];
foreach ($map as $key => $value) {
    echo "$key = $value\n";
}

// By-reference value binding mutates the source array element.
$nums = [1, 2, 3];
foreach ($nums as &$value) {
    $value *= 2;
}

Use foreach ($arr as $key => &$value) when both the key and a mutable element reference are needed. The key itself cannot be bound by reference. By-reference value binding is currently supported only for array sources; foreach ($iterator as &$value) over Iterator, IteratorAggregate, or iterable-typed values is rejected at compile time. Use an array source or iterate by value when consuming Traversable objects.

Untyped, mixed, and union-typed sources are dispatched at runtime. If the runtime value is an indexed or associative array, both by-value and by-reference value binding are supported. If the runtime value is an Iterator or IteratorAggregate, it is iterated by value; by-reference value binding over Traversable objects is rejected. Non-iterable runtime values produce a fatal diagnostic.

foreach also accepts any object that implements the built-in Iterator interface (current, key, next, valid, rewind) or the IteratorAggregate interface (getIterator(): Traversable):

<?php
class Range implements Iterator {
    private int $current;
    private int $end;
    public function __construct(int $start, int $end) {
        $this->current = $start;
        $this->end = $end;
    }
    public function rewind(): void {}
    public function valid(): bool { return $this->current < $this->end; }
    public function current(): mixed { return $this->current; }
    public function key(): mixed { return $this->current; }
    public function next(): void { $this->current = $this->current + 1; }
}

foreach (new Range(0, 5) as $i) {
    echo $i;
}

The loop calls rewind() once, then on each iteration: valid() to test continuation, current() and key() to bind the loop variables, and next() after the body. Method dispatch uses class vtables for concrete iterator classes and interface metadata for Iterator/IteratorAggregate typed values. The iterable pseudo-type accepts arrays and these Traversable objects.

break / continue

<?php
for ($i = 0; $i < 100; $i++) {
    if ($i == 5) { break; }
    if ($i % 2 == 0) { continue; }
    echo $i . " ";
}
// Output: 1 3

Multi-level exits are supported with positive integer literal depths:

<?php
for ($row = 0; $row < 3; $row++) {
    for ($col = 0; $col < 3; $col++) {
        if ($row == 1 && $col == 1) {
            break 2;       // leaves both loops
        }
    }
}

The level counts enclosing loops and switch statements, matching PHP. break; and continue; are equivalent to break 1; and continue 1;. Inside a finally block, break and continue may only target loops or switches created inside that same finally; jumping out of finally is rejected, matching PHP.

switch / case / default

Standard PHP switch with fall-through semantics. Use break to prevent fall-through.

<?php
$x = 2;
switch ($x) {
    case 1:
        echo "one";
        break;
    case 2:
        echo "two";
        break;
    default:
        echo "other";
        break;
}

Fall-through example:

<?php
$x = 1;
switch ($x) {
    case 1:
    case 2:
        echo "one or two";
        break;
    default:
        echo "other";
}

match expression

PHP 8 style match. No fall-through, returns a value, uses strict comparison (===).

<?php
$x = 2;
$result = match($x) {
    1 => "one",
    2 => "two",
    3 => "three",
    default => "other",
};
echo $result; // two

If no arm matches and there is no default, elephc aborts with a fatal runtime error.

try / catch / finally / throw

<?php
class DivisionByZeroException extends Exception {}

function divide($left, $right) {
    if ($right == 0) {
        throw new DivisionByZeroException();
    }
    return intdiv($left, $right);
}

try {
    echo divide(10, 2) . PHP_EOL;
    echo divide(10, 0) . PHP_EOL;
} catch (DivisionByZeroException $e) {
    echo "caught" . PHP_EOL;
} finally {
    echo "cleanup" . PHP_EOL;
}

Supported subset:

• built-in Error and Exception classes and the Throwable interface are available without declaring them
• Error and Exception provide $message, $code, __construct($message = "", $code = 0), getMessage(), and getCode()
• the SPL exception hierarchy is built-in: LogicException, BadFunctionCallException, BadMethodCallException, DomainException, InvalidArgumentException, LengthException, OutOfRangeException, RuntimeException, OutOfBoundsException, OverflowException, RangeException, UnderflowException, UnexpectedValueException. Each is a marker subclass that inherits the constructor, $message, and getMessage() from Exception. Catch a specific type (InvalidArgumentException), an intermediate parent (LogicException), or the root (Exception/Throwable)
• throw <expr>; where <expr> has an object type implementing Throwable
• throw <expr> can also be used inside expressions such as ?? and ternaries
• catch (ClassName $e) and catch (TypeA | TypeB $e) for multi-catch
• catch (Exception), catch (Error), or another throwable type without binding the exception variable
• catch types must extend or implement Throwable
• multiple catch clauses
• try { ... } finally { ... }
• return, break, and continue run enclosing finally blocks before leaving
• break and continue written inside a finally block cannot target an outer loop or switch