Struct Type¶
A struct is a value type that groups named fields together, as in C, Go, Rust, or Swift. Unlike a class instance in most object-oriented languages, a struct value is typically copied by value on assignment or when passed to a function, is allocated inline rather than behind a pointer, and carries no built-in identity or inheritance: two structs are simply equal when their fields are equal.
Structs are commonly used for small, self-contained data, such as a 2D point or an RGB color, where the overhead of heap allocation and reference semantics would be wasted.
PHP has no struct type. Every class instance is a heap-allocated object with reference semantics: assigning an object to a new variable, or passing it to a function, copies the reference, not the object’s contents, so mutations through one variable are visible through the other. A PHP class can imitate the field-grouping role of a struct, but not its value semantics; achieving copy-on-assign behavior requires implementing __clone() and calling it manually, or declaring the class readonly.
The closest notion ofa struct type is stdClass which is an empty class, with dynamic typeless properties, which may be populated at will, or an array: both notions are actually accessible to the other with casting.
<?php
class Point {
public function __construct(public float $x, public float $y) {}
}
$a = new Point(1.0, 2.0);
$b = $a; // copies the reference, not the object
$b->x = 99.0; // also changes $a->x: PHP objects have reference semantics
?>
See also Record in Wikipedia.
Related : Class, Record Type, Value Type, __clone() Method, Readonly
