PHP: Chaining Method Calls [duplicate] - php

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Closed 11 years ago.
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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.

Answer 2

The above example (the first one) is something called chaining. Here's a regular class:
class a_class
{
public function method_a()
{
echo 'method a';
}
public function method_b()
{
echo ' - method b';
}
}
You'd call those like this:
$class = new a_class();
$class->method_a();
$class->method_b();
Which would echo 'method a - method b'. Now to chain them, you'd return the object in the methods:
class a_class
{
public function method_a()
{
echo 'method a';
return $this;
}
public function method_b()
{
echo ' - method b';
return $this;
}
}
You'd call those like this:
$class = new a_class();
$class->method_a()->method_b();
Which would also echo 'method a - method b'.
Although I have returned the object in the last method - you strictly wouldn't need to, only the preceding methods require that for chaining.