Access Level to certain class must be public error in PHP

问题

I created this class

<?php
    abstract class Validator{
        public $_errors = array();
        abstract public function isValid($input);

        public function _addErrors($message){
            $this->_errors = $message;
        }

        public function getErrors(){
            return $this->_errors;
        }


        public function getMessage(){
            return $this->message;
        }
    }

    class Validator_NoSpaces extends Validator{

        public function __construct($value){
            $this->isValid($value);
        }
        public function isValid($value){
                if (preg_match('/\s/', $value)){
                $this->_addErrors("Spaces are not allowed");
                return false;
            }
            return true;
        }       
    }

    class Validator_MinimumLength extends Validator{

        protected $_minLength;
        protected $value;

        public function __construct($value ,$minLength=8){
            $this->_minLength = $minLength;
            $this->value = $value;
            $this->isValid($value);
        }

        public function isValid($input){
             if (strlen($input) > $this->_minLength) {
                 return true;
            }else{
                $this->_addErrors("Input must be at least {$this_minLength}");
                return false;
          }
        }
    }

    class Form_Element_Validators extends Validator{

        protected $_validators = array();

    public function addValidator(Validator $validator)
    {
        $this->_validators[] = $validator;
    }

    public function getValidators()
    {
        return $this->_validators;
    }

    protected function _addErrors(array $errors)
    {
        foreach ($errors as $error) {
            $this->_addErrors($error);
        }
    }

    public function hasErrors()
    {
        return (count($this->getErrors()) !== 0);
    }

    public function isValid($input)
    {
        foreach ($this->_validators as $validator) {
            if (!$validator->isValid($input)) {
                $this->_addErrors($validator->getErrors());
            }
        }
        return !$this->hasErrors();
    }

    }

    class Form_Element extends  Form_Element_Validators{

        public function __construct($value){
              $this->addValidator(new Validator_NoSpaces($value));
              $this->addValidator(new Validator_MinimumLength($value));
        }
    }

for Validation purposes, but it kept giving me this error

Fatal error: Access level to Form_Element_Validators::_addErrors() must be public (as in class Validator) in C:\xampp\htdocs\beatbeast\includes\Db\Validators.php on line 91

But the instance variable in this class $_errors is declared public, I don't get it why I am receiving this error.

回答1:

Youre getting that error because the visibility of the method must be the same or less restrictive than that of it its definition on a parent class. In this case you have addErrors as public on your abstract class and are attempting to make it protected on a child class.

回答2:

As others have mentioned, you can't make a sub class method more restrictive than the parent; this is because sub classes are supposed to be a valid replacement for their parent class.

In your particular case, I would change the visibility of all methods and properties that start with an underscore to protected.

回答3:

You've specify the protected access to the protected function _addErrors(array $errors) method of Form_Element_Validators class. So change it to public.

Edit:

Have you noticed? The sub class method (overridden method) is defined with Type Hinting. Please keep the same parameter type for both; super-class and sub-class method.

 abstract class Validator{
        public $_errors = array();
        abstract public function isValid($input);

        public function _addErrors(array $message){
            $this->_errors = $message;
        }
        ....