Class name must be a valid object or a string - php

Question

I am trying to inject one class (a simple PHP class) into another (an ORM\Entity annotated class), and getting an error, but I cannot discover the source. Looking at the code I feel like I am doing everything correctly, yet I cannot solve this error.
Here is the relevant code:
First, the class ORM\Entity where I want to inject the ErrorConstants class:
use Base\Model\Constants\ErrorConstants;
/**
* #ORM\Entity ...
*/
class CwPackagePeriod extends AbstractRestEntity
public $errors;
public function __construct()
{
parent::__construct();
$this->errors = new ErrorConstants();
}
}
The ErrorConstants class is a simple class that contains a list of error constants:
class ErrorConstants
{
public const ERR_MISSING = 'Record could not be found.';
}
The error occurs when I try to throw an exception in the CwPackagePeriod class if an integer value is out of bounds on a setter:
throw new InvalidOrMissingParameterException(
sprintf($this->errors::ERR_MISSING)
);
The error is the following:
Class name must be a valid object or a string
The AbstractRestEntity class does not contain any reference to ErrorConstants, and when I add the reference there, nothing changes with respect to the error. What am I doing wrong?

Answer 1

As u_mulder noted constants refer to class, not to class instance. In order to properly get the constants from your class you could use something like that in your ErrorConstants class:
public function getConstants()
{
$reflectionClass = new \ReflectionClass($this);
return $reflectionClass->getConstants();
}
then in your CwPackagePeriod class:
public function __construct()
{
parent::__construct();
$errorConstants = new ErrorConstants();
$this->errors = $errorConstants->getConstants();
}
...
throw new InvalidOrMissingParameterException(
sprintf($this->errors['ERR_MISSING']);
);
Of course the simplest solution would be to use just:
throw new InvalidOrMissingParameterException(
sprintf(ErrorConstants::ERR_MISSING);
);
Finally I would like to note, although it is not very intuitive, you CAN indeed use $this->errors::ERR_MISSING to get a constant. The reason because you get this error is probably because $this->errors is not defined in that part of code for some reason.