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Implementing static methods

From: Object-Oriented Programming with PHP

Video: Implementing static methods

Static methods are similar to regular methods in a number of ways. The naming convention is the same, they can have a visibility scope, and static methods can return values. However, static methods cannot use the pseudo variable $this to get properties, as it refers to the current object. If you want to try anyway, you can, but you will get a fatal error. Instead, use the self keyword, which refers to the current class. This sounds a bit abstract, so I'll demonstrate a static method by implementing an address type id validator.

Implementing static methods

Static methods are similar to regular methods in a number of ways. The naming convention is the same, they can have a visibility scope, and static methods can return values. However, static methods cannot use the pseudo variable $this to get properties, as it refers to the current object. If you want to try anyway, you can, but you will get a fatal error. Instead, use the self keyword, which refers to the current class. This sounds a bit abstract, so I'll demonstrate a static method by implementing an address type id validator.

I'm going to open the Address class, and then start declaring a static method. Like static properties, I'll need to include the static keyword. Static public function isValidAddressTypeId with one argument ($address_type_id). Add the documentation, Determine if an address type is valid. We'll take an integer and return boolean.

To validate, check to see if the address _type_id is in the array keys of valid address types. return array_key_exists. The key is the address_type_id. The array will be self::$valid_address_types. Save, then test the validator by opening the demo script, navigating to the end, and writing a quick test. Start with the title, describing what you're testing. echo

Testing address_type_ID validation.

Next, use a for loop to test the whole numbers 0 through 4. Start with a div, and display the id. for ($id = 0; id <= 4; id++), echo double quotes

$id is. On the next line, use a ternary operator to display whether the current id is valid or invalid. echo Address:: IsValidAddressTypeId, Valid else Invalid. close the div. Save the demo, and return to the browser. Refresh to see the results.

Id 0 and 4 are invalid, while ID's 1, 2, and 3 are valid. Now that you have a mechanism of validating an address type, you can improve the Address class by storing the address_type_id in the object, but only allowing valid IDs to be stored. Return to the Address class. Navigate the properties. Then, add a new property for address type id after the address_id. protected address_type_id.

The next thing I'm going to do is declare a new method for setting an address_type_id in an address. If I created it as a public method, anything could set the address type, which I don't want to allow. Instead, I'll protect it, and use the magic _get and _set methods to allow access. Going back to the code, navigate to the end of the file, and start declaring a new function. protected function _ setAddressTypeId, which accepts one argument, address_type_id, in the documentation. If valid, set the address_type_id. And, the parameter is an integer.

Next, check to see if the address type is valid. You can also use the self keyword, as the self keyword refers to the class of the object. if self::isvalidAddressTypeId. Set the protected value. this->address_type_id = $address_type_id. Now that you have a way to set the address_type_id, add the clue necessary for public interface. The Magic _get method needs no additional configuration, but the _set method does. Navigate the Magic _set method. Then, at the top, add an if statement to check for the property name address_type_id.

Only set valid address type id, if address_type_id is == $name, this->setAddressType value. Then return. Save. Then return to the demo script, navigate to the first creation of the address object, and add an address_type_id, to it. address->address_ type_id = 1. Save the demo.

Now return to your browser, and refresh. Scroll up to the Setting property section, and you will see the newly set address_type_id. We now have a way of validating user input, and only setting good values. By making the validator static, we can use it outside of the address class. This is useful for doing things like validating form submissions. The address class is growing nicely, but there's still a placeholder for the database lookup. In a moment, I'll show you how to connect to the database using a custom class.

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This video is part of

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Object-Oriented Programming with PHP

37 video lessons · 17930 viewers

Jon Peck
Author

 
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  1. 4m 10s
    1. Welcome
      39s
    2. Exercise files
      2m 16s
    3. What you should know
      1m 15s
  2. 7m 47s
    1. What is an object?
      2m 6s
    2. What is a class?
      2m 7s
    3. Why should you use object-oriented programming?
      2m 14s
    4. The history of object-oriented PHP
      1m 20s
  3. 16m 40s
    1. Defining a class
      2m 58s
    2. Defining class properties
      3m 26s
    3. Creating a method and exploring object context with $this
      2m 50s
    4. Instantiating an object and accessing its contents
      3m 19s
    5. Specifying the visibility scope
      4m 7s
  4. 15m 51s
    1. What is a magic method, and do I need one?
      2m 23s
    2. Overloading property access
      6m 37s
    3. Customizing object construction
      4m 34s
    4. Standardizing object rendering as a string
      2m 17s
  5. 20m 54s
    1. Using the static keyword
      3m 36s
    2. Leveraging scope resolution operators
      1m 10s
    3. Setting constant values
      2m 47s
    4. Implementing static methods
      5m 43s
    5. Creating a database class
      7m 38s
  6. 26m 19s
    1. Extending your class
      6m 8s
    2. Abstracting classes
      5m 57s
    3. Sharing interfaces using polymorphism
      4m 39s
    4. Overriding methods, properties, and constants
      3m 25s
    5. Cloning and comparing objects
      2m 51s
    6. Referencing objects
      3m 19s
  7. 14m 52s
    1. Leveraging standard class objects
      2m 42s
    2. Retrieving objects from the database
      5m 41s
    3. Error handling with exceptions
      2m 6s
    4. Customizing PHP exceptions
      4m 23s
  8. 8m 2s
    1. Identifying the singleton pattern
      1m 42s
    2. Using the factory method pattern
      1m 51s
    3. Implementing a strategy pattern
      4m 29s
  9. 2m 57s
    1. Looking forward to namespaces
      47s
    2. Next steps
      1m 6s
    3. Goodbye
      1m 4s

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