example.php

<?php

trait VerifyPrecondition {
    protected $parent;
    protected function verifyPrecondition($method, array $args) {
        $objs = [new ReflectionMethod($this->parent, $method)];
        foreach ((new ReflectionObject($this->parent))->getInterfaces() as $iface) {
            if ($iface->hasMethod($method)) {
                $objs[] = $iface;
        }
        $parent = $objs[0]->getDeclaringClass()->getParentClass();
        while ($parent) {
            if ($parent->hasMethod($method)) {
                $rm = $parent->getMethod($method);
                $objs[] = $rm;
                $parent = $rm->getDeclaringClass()->getParentClass();
            } else {
                $parent = false;
            }
        }
        while ($r = array_shift($objs)) {
            $r = new ReflectionMethod($obj, $method);
            $scope = [];
            foreach ($r->getParameters() as $arg) {
                // add additional checks here
                $scope[$arg->getName()] = isset($args[$arg->getPosition()]) ? $args[$arg->getPosition()] : $arg->getDefaultValue();
            }
            foreach ($r->getAnnotations("precondition") as $annotation) {
                if (!$annotation->getValue($scope, $this->parent)) {
                    throw new ConstraintViolationException(...);
                }
            }
        }
    }
}

interface Foo {
    <precondition($a > 0)>
    <precondition($div > 0)>
    public function getRemainder(int $a, int $div): int;
}

class FooImpl implements Foo{
    public function getRemainder(int $a, int $div): int {
        return $a % $div;
    }
}

class FooImpl2 implements Foo {
    <precondition($a != $div)>
    public function getRemainder(int $a, int $div): int {
        return $a % $div;
    }
}

class PreconditionVerifierForFoo implements Foo {
    use VerifyPrecondition;
    public function __construct(Foo $foo) {
        $this->parent = $foo;
    }
    public function getRemainder(int $a, int $div): int {
        $this->verifyPreconditions(__METHOD__, func_get_args());
        return $this->parent->getRemainder($a, $div);
    }
}

$foo = new FooImpl;
$foo->getRemainder(5, 0); // 0

$verifiedFoo = new PreconditionVerifierForFoo($foo);
$verifiedFoo->getRemainder(5, 5); // 0
$verifiedFoo->getRemainder(5, 0); // ConstraintViolationException

$verifiedFoo2 = new PreconditionVerifierForFoo(new Foo2);
$verifiedFoo2->getRemainder(5, 5); // ConstraintViolationException

reflection.php

<?php

class ReflectionAnnotation {
    /**
     * Get the name of the annotation
     */
    public function getName(): string {}
 
    /**
     * Executes the expression using the supplied scope and object context
     */
    public function getValue(array $scope = [], object $context = null): mixed {}

    /**
     * Get the raw AST in array form
     */
    public function getAst(): array {}
}

$r = new ReflectionMethod($obj, $method);
$annotations = $r->getAnnotations(); // return all
$annotations = $r->getAnnotations($name); // return all named $name