Question

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PHP method chaining?

I occasionally see some php applications use classes like that:

$Obj = new Obj();
$Obj->selectFile('datafile.ext')->getDATA();

The example above gets the contents of the selected file then returns them ( just an example );

Well, before i decided to ask you how can I do this, I tried this:

class Someclass {
    public function selectFile( $filename  ) { 
       $callAclass = new AnotherClass( $filename );
       return $callAclass;
    }

    // Other functions ...
}

class AnotherClass {
    protected $file_name;

    public function __construct ( $filename ) { $this->file_name = $filename; }
    public function getDATA ( ) {
        $data = file_get_contents( $this->file_name );
        return $data;

    } 

    // funcs , funcs, funcs ....

}

Is that the right way to accomplish this task? And please tell me what these classes are called.

Answer 1

It’s called method chaining. Have a look at this question on SO.

Here’s a way you can do what you’re trying to achieve:

class File 
{
    protected $_fileName;

    public function selectFile($filename) 
    { 
        $this->_fileName = $filename; 
        return $this;
    }

    public function getData()
    {
        return file_get_contents($this->_fileName);
    }
}


$file = new File();
echo $file->selectFile('hello.txt')->getData();

Notice we return $this in the selectFile, this enables us to chain another method onto it.