src/Reflection/ReflectionClass.php
public function implementsInterface(string $interfaceName) : bool
    {
        return in_array(ltrim($interfaceName, '\\'), $this->getInterfaceNames(), true);
    }
public function implementsInterface(string $interfaceName) : bool
    {
        return in_array(ltrim($interfaceName, '\\'), $this->getInterfaceNames(), true);
    }
Checks whether this class implements the given interface.

@link https://php.net/manual/en/reflectionclass.implementsinterface.php