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Cloning and comparing objects

From: Object-Oriented Programming with PHP

Video: Cloning and comparing objects

Sometimes, you will want to make a copy of an object. There are many reasons to do this, including making a backup before performing an operation, or as a shortcut for defining a similar object. To create a copy of an object, use the clone keyword. As a demonstration, make a copy of the park address, open the demo script, and navigate to the bottom. Add the following lines: echo

Cloning AddressPark

$address_park_clone = clone $address_park. And then, we'll debug the clone.

Cloning and comparing objects

Sometimes, you will want to make a copy of an object. There are many reasons to do this, including making a backup before performing an operation, or as a shortcut for defining a similar object. To create a copy of an object, use the clone keyword. As a demonstration, make a copy of the park address, open the demo script, and navigate to the bottom. Add the following lines: echo

Cloning AddressPark

$address_park_clone = clone $address_park. And then, we'll debug the clone.

To check the differences between clones, I'm going to compare two objects. Comparing objects is a lot like comparing primitives, such as strings and floats. I can use the comparison operator, double equals (==), which will check to see if the properties are the same. If I need to be more strict, I can use the identity operator, triple equals (===), to also check if both objects are instances of the same class. At the end of the script, add echo $ address_park_clone_ is. And then, a ternary statement. $address_park == $address_park_clone ? : not ] a copy of $address_park. Save the demo, and refresh the browser.

Visually, every property is the same, and the final line indicates this. However, the time created isn't necessarily the same, especially if one object is based on an old record from the database. To deal with this, I'm going to use the _ clone() magic method in the address class. If the method exists, it will be called after object cloning. As an example, I am going to use this to reset the time created. Let's go back to the address class. Then, after the properties, add the clone method, which takes no arguments. Remember to add proper documentation.

For the demonstration, I will explicitly set the time_created and time_updated to obvious values. Save, then switch to the browser, and refresh. The time_updated and created have been set to the new values, and the final line states that $address_park_clone is not a copy of $address_park. Return to the clone function, and set time_ created = time, and time_updated = Null. Now that I've demonstrated object cloning, I am going to discuss how to reference objects.

Referencing can be similar to cloning, but there are enough differences to make it worth exploring on its own.

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Object-Oriented Programming with PHP

37 video lessons · 17763 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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