Question 40456 in PHP Question posted in
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Calling Sub Class Method On Parent PHP Class

I have 2 PHP class that related each other, rather than using __construct, I tryin to using extends to combine these 2 class. But why sub class method cant called from parent class? There’s no either result or error displayed but warning about reach memory limit.

here my example code:

<?php
class Me
{

    public $you;

    public function __construct()
    {
        $this->you = new You;
    }

    public function Hi()
    {
        return 'Hi You';
    }

    public function WhatYouSaid()
    {
        return $this->you->Me();
    }

}

class You extends Me
{

    public function Me()
    {
        return 'Yes Me';
    }
}

$talk = new You;
print_r($talk->WhatYouSaid());

https://onlinephp.io/c/3d84d

I received error:

Fatal error: Allowed memory size of xxx bytes exhausted (tried to allocate xx bytes)

Based on @Nigel Ren answer i found solution here another example:

<?php
 class DataValidate {

    public $data;   

  public function __construct() {
     $this->data = new Data;
  }

public  function inputValidate($newData)
    {
        // verifying
        if ($this->data->get_data($newData['Identifier'], 'nameId'))
        {
            return false; // alredy exists
        }
        return $newData;
    }
    
}




class Data {

    public $db; 
    public $validate;

  public function __construct() {
     $this->db = new Database;
     $this->validate = new DataValidate; 
  } 

public  function get_data($identifier, $col)
        {
            return $this->db->select($identifier, $col='*');
        }
        
public  function inputValidate($newData)
{
    
    return $this->validate->inputValidate($newData);
}
}



$data = new Data;
print_r($data->inputValidate($some_id));
Tags:

2

Answers


  1. 0

    Each time you create a new object or type You, this calls the constructor in Me. This then creates a new object of type You, this calls the constructor in Me …

    So you quickly run out of memory as it’s creating loads of new objects.

    There is also a case of having a different method name, I have assumed that you meant to have the same name for the 2 output methods. You wouldn’t normally introduce a new method in a sub class.

    So this code just calls the method on the current object rather than creating a new object to use…

    class Me {
    public  function Hi()
    {
        return 'Hi You';
    }

    public  function WhatYouSaid()
    {
        return $this->Hi();
    }   
    
}

class You extends Me{

    public  function Hi()
    {
        return 'Yes Me';
    }
}

$talk = new You;
print_r($talk->WhatYouSaid());

    Edit:
    If you just want to make the idea of calling a method from another class, then using extend doesn’t help you at all. It just needs to be a class which has a public method to allow you to call.

    Then you create an instance of Me rather than You and make the call…

    class Me
{
    public $you;

    public function __construct()
    {
        $this->you = new You;
    }

    public function Hi()
    {
        return 'Hi You';
    }

    public function WhatYouSaid()
    {
        return $this->you->Me();
    }
}

class You
{
    public function Me()
    {
        return 'Yes Me';
    }
}

$talk = new Me;
print_r($talk->WhatYouSaid());
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  2. 0

    Actually the problem is that, each time you try to create a Me object, it instantiate a You object (as you set in Me‘s constructor).

    As You extend Me, when you instantiate a You object, it starts by executing the code in Me‘s constructor, so you go into a non-stop loop. Then you run out of memory.

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