Returntype Covariance¶
PHP 7.4 added the support of return type covariance. The return type of a child class may be more strict than the one of the parent.
In PHP 7.3, the child method must have the same return type than the parent.
PHP code¶
<?php
interface i {}
interface j extends i {}
class x {
function foo() : i {
}
}
class y extends x {
function foo() : j {
}
}
var_dump(new y);
?>
Before¶
PHP Fatal error: Declaration of y::foo(): j must be compatible with x::foo(): i in /codes/covarianceReturntype.php on line 17
Fatal error: Declaration of y::foo(): j must be compatible with x::foo(): i in /codes/covarianceReturntype.php on line 17
After¶
object(y)#1 (0) {
}
PHP version change¶
This behavior changed in 7.4
