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Object-Oriented Programming with PHP
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Implementing static methods


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Object-Oriented Programming with PHP

with Jon Peck

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.
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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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Object-Oriented Programming with PHP
1h 57m Intermediate Sep 26, 2012 Updated Apr 10, 2013

Viewers: in countries Watching now:

Whether you're enhancing or optimizing existing code or just starting from scratch, there's never a better time to start integrating object-oriented design techniques. This course shows how to integrate the principles of object-oriented programming into the build of a PHP-driven web page or application. After an overview of what objects and classes are and why they should be used, author Jon Peck dives into creating and instantiating objects, then defining the class relationships and interactions that will form the basis of your coding arsenal. The course also shows how to leverage PHP objects and implement design patterns, and looks at steps you can take to continue adding to your programming tool belt.

Topics include:
  • Historical overview of object-oriented PHP
  • Defining classes
  • Creating a method/object context with $this
  • Accessing classes without instantiation
  • Creating a database class
  • Extending and abstracting classes
  • Cloning and comparing objects
  • Error handling with exceptions
  • Implementing design patterns, such as the factory and strategy patterns
Subjects:
Developer Programming Languages
Software:
PHP
Author:
Jon Peck

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.

Find answers to the most frequently asked questions about Object-Oriented Programming with PHP.


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Q: I'm not seeing warnings or errors in my environment like the video; why not?
A: Your PHP configuration is probably configured not to show them to you. This is often true on commercial web hosts and is often the default. Fortunately, there are multiple ways of resolving this.

The easiest way would be to explicitly enable error reporting at the top of the PHP script you wish to debug.

error_reporting(E_ALL | E_STRICT);
ini_set('display_errors', 1);

Alternatively, if you have access to your php.ini file and you want to always have error reporting on, change error_reporting = to a development friendly value of

error_reporting = E_ALL | E_STRICT

then change display_errors = to

display_errors = On

Finally, if access to the php.ini file is not available, you can add the following directives to your .htaccess or VirtualHost configuration for Apache:

php_value error_reporting 32767
php_value display_errors 1

If you would like a development optimized development environment like the one utilized in this course, see Up and Running with Linux for PHP Developers, here in the lynda.com online training library.

Q: This course was updated on 4/10/2013. What changed?

A: The author rerecorded some of the tutorials to add more background information and better graphics.

 

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