Where and why do we use __toString() in PHP?

Question

I understand how it works but why would we practically use this?

Answer 1

The __toString method allows a class to decide how it will react when it is treated like a string

http://www.php.net/manual/en/language.oop5.magic.php#language.oop5.magic.tostring

Answer 2

You don't "need" it. But defining it allows your object to be implicitly converted to string, which is convenient.

Having member functions that echo directly is considered poor form because it gives too much control of the output to the class itself. You want to return strings from member functions, and let the caller decide what to do with them: whether to store them in a variable, or echo them out, or whatever. Using the magic function means you don't need the explicit function call to do this.

Answer 3

It's just a standardized method to produce a string representation of an object. Your random_method approach works if you assume all objects in your program uses that same method, which might not be the case if you use third party libraries.

You don't need the magic method, but it provides convenience, as you'll never really have to call it explicitly.

Also, if PHP should internally ever want to turn your object into text, it knows how to do that.

Answer 4

You don't have to specifically call the toString method. When ever you print the object toString is being called implicitly. Any other method would have to be called explicitly.

Answer 5

In addition to all existing answers, here's an example, :

class Assets{

  protected 
    $queue = array();

  public function add($script){
    $this->queue[] = $script;
  }

  public function __toString(){    
    $output = '';    
    foreach($this->queue as $script){
      $output .= '<script src="'.$script.'"></script>';
    }    
    return $output;
  }

}


$scripts = new Assets();

It's a simple class that helps you manage javascripts. You would register new scripts by calling $scripts->add('...').

Then to process the queue and print all registered scripts simply call print $scripts;.

Obviously this class is pointless in this form, but if you implement asset dependency, versioning, checks for duplicate inclusions etc., it starts to make sense (example).

The basic idea is that the main purpose of this object is to create a string (HTML), so the use of __toString in this case is convenient...

Answer 6

__toString allows you to define the output when your object is converted to a string. This means that you can print the object itself, rather than the return value of a function. This is frequently more convenient. See the manual entry.