{"id":103,"date":"2021-03-08T00:19:39","date_gmt":"2021-03-08T00:19:39","guid":{"rendered":"https:\/\/phptutorial.net\/?page_id=103"},"modified":"2025-04-07T11:27:52","modified_gmt":"2025-04-07T11:27:52","slug":"php-abstract-class","status":"publish","type":"page","link":"https:\/\/www.phptutorial.net\/php-oop\/php-abstract-class\/","title":{"rendered":"PHP Abstract Class"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you will learn how to use the PHP abstract class to define an interface for other classes to extend.<\/p>\n\n\n\n

Introduction to the PHP abstract class #<\/a><\/h2>\n\n\n\n

An abstract class is a class<\/a> that cannot be instantiated. Typically, an abstract defines an interface for other classes to extend. <\/p>\n\n\n\n

To define an abstract class, you add the abstract<\/code> keyword as follows:<\/p>\n\n\n

<?php<\/span>\n\nabstract<\/span> class<\/span> className<\/span>\n<\/span>{\n   \/\/ ...<\/span>\n}<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
An abstract class can have properties and methods as a regular class. But it cannot be instantiated.<\/p>\n\n\n\n
Similar to an abstract class, an abstract method is a method that does not have an implementation. To define an abstract method, you also use the abstract<\/code> keyword before the method signature like this<\/p>\n\n\n
abstract<\/span> function<\/span> methodName<\/span>(arguments)<\/span><\/span>;<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
In most cases, an abstract class will contain at least one abstract method though it is not required. If a class contains one or more abstract methods, it must be an abstract class.<\/p>\n\n\n\n
PHP abstract class example #<\/a><\/h2>\n\n\n\n
The following example defines an abstract class called Dumper<\/code> that has an abstract method dump()<\/code>:<\/p>\n\n\n
<?php<\/span>\n\nabstract<\/span> class<\/span> Dumper<\/span> \n<\/span>{\n\tabstract<\/span> public<\/span> function<\/span> dump<\/span>($data)<\/span><\/span>;\n}<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
To dump information on the web, you can extend the Dumper<\/code> class. <\/p>\n\n\n\n
The following defines the WebDumper<\/code> class that extends the Dumper<\/code> class. Since the Dumper<\/code> class has the dump() abstract method, the WebDumper<\/code> class needs to implement the dump()<\/code> method:<\/p>\n\n\n
<?php<\/span>\n\nabstract<\/span> class<\/span> Dumper<\/span>\n<\/span>{\n\tabstract<\/span> public<\/span> function<\/span> dump<\/span>($data)<\/span><\/span>;\n}\n\nclass<\/span> WebDumper<\/span> extends<\/span> Dumper<\/span>\n<\/span>{\n\tpublic<\/span> function<\/span> dump<\/span>($data)<\/span>\n\t<\/span>{\n\t\techo<\/span> '<pre>'<\/span>;\n\t\tvar_dump($data);\n\t\techo<\/span> '<\/pre>'<\/span>;\n\t}\n}<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
The following creates a new instance of the WebDumper<\/code> class and call the dump()<\/code> method:<\/p>\n\n\n
$webDumper = new<\/span> WebDumper();\n$webDumper->dump('PHP abstract class is awesome!'<\/span>);<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
If you open the web browser, you’ll see the message is wrapper inside a <pre> tag:<\/p>\n\n\n
string(30<\/span>) \"PHP abstract class is awesome!\"<\/span><\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Later, if you want to dump the information to the command line, you can define a class e.g., ConsoleDumper<\/code> that extends the Dumper<\/code> class:<\/p>\n\n\n
<?php<\/span>\n\nclass<\/span> ConsoleDumper<\/span> extends<\/span> Dumper<\/span>\n<\/span>{\n\tpublic<\/span> function<\/span> dump<\/span>($data)<\/span>\n\t<\/span>{\n\t\tvar_dump($data);\n\t}\n}<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
The dump()<\/code> method of the ConsoleDumper<\/code> calls the var_dump()<\/code> function to dump the information to the command line.<\/p>\n\n\n\n
This UML diagram illustrates the relationship between the Dumper, WebDumper, and ConsoleDumper classes:<\/p>\n\n\n\n
\"\"<\/figure><\/div>\n\n\n\n
The following defines a DumperFactory<\/code> class that has a static method<\/a> getDumper()<\/code>.  <\/p>\n\n\n\n
The getDumper()<\/code> method returns a new WebDumper<\/code> object if the script is executed on the webserver and ConsoleDumper<\/code> object if the script is executed on the command line:<\/p>\n\n\n
class<\/span> DumperFactory<\/span>\n<\/span>{\n\tpublic<\/span> static<\/span> function<\/span> getDumper<\/span>()<\/span>\n\t<\/span>{\n\t\treturn<\/span> PHP_SAPI === 'cli'<\/span>\n\t\t\t? new<\/span> ConsoleDumper()\n\t\t\t: new<\/span> WebDumper();\n\t}\n}<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
The following uses the DumperFactory<\/code> to get a Dumper based on where the script runs and show a message:<\/p>\n\n\n
$dumper = DumperFactory::getDumper();\n$dumper->dump('PHP abstract class is awesome!'<\/span>);<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
If you execute the script on the web browser, you’ll see the following message wrapped nicely in a <pre> tag:<\/p>\n\n\n
string(30<\/span>) \"PHP abstract class is awesome!\"<\/span><\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
However, if you run the script using PHP CLI, you’ll only see the message without the <pre><\/code> tag.<\/p>\n\n\n\n
Put it all together:<\/p>\n\n\n
<?php<\/span>\n\nabstract<\/span> class<\/span> Dumper<\/span>\n<\/span>{\n\tabstract<\/span> public<\/span> function<\/span> dump<\/span>($data)<\/span><\/span>;\n}\n\nclass<\/span> WebDumper<\/span> extends<\/span> Dumper<\/span>\n<\/span>{\n\tpublic<\/span> function<\/span> dump<\/span>($data)<\/span>\n\t<\/span>{\n\t\techo<\/span> '<pre>'<\/span>;\n\t\tvar_dump($data);\n\t\techo<\/span> '<\/pre>'<\/span>;\n\t}\n}\n\nclass<\/span> ConsoleDumper<\/span> extends<\/span> Dumper<\/span>\n<\/span>{\n\tpublic<\/span> function<\/span> dump<\/span>($data)<\/span>\n\t<\/span>{\n\t\tvar_dump($data);\n\t}\n}\n\nclass<\/span> DumperFactory<\/span>\n<\/span>{\n\tpublic<\/span> static<\/span> function<\/span> getDumper<\/span>()<\/span>\n\t<\/span>{\n\t\treturn<\/span> PHP_SAPI === 'cli'<\/span>\n\t\t\t? new<\/span> ConsoleDumper()\n\t\t\t: new<\/span> WebDumper();\n\t}\n}\n\n$dumper = DumperFactory::getDumper();\n$dumper->dump('PHP abstract class is awesome!'<\/span>);<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Summary #<\/a><\/h2>\n\n\n\n
  • An abstract class cannot be instantiated. It provides an interface for other classes to extend.<\/li>
  • An abstract method doesn’t have an implementation. If a class contains one or more abstract methods, it must be an abstract class.<\/li>
  • A class that extends an abstract class needs to implement the abstract methods of the abstract class.<\/li><\/ul>\n
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If a class extends<\/a> an abstract class, it must implement all abstract methods or itself be declared abstract. <\/p>\n\n\n\n