Jose Diaz-Gonzalez

Since upgrading to CakePHP 3, you may have noticed a few changes. Yes, it’s faster, better for your cholesterol, and likely good for your Vitamin D intake ¹. However, what I’m referring to is the nicer debugging output.

Typically when you debug an object in PHP, you use something like print_r() or var_dump(). With scalar types - int, float, string and bool - you’ll get a pretty simple representation:

php > $i = 1;
php > var_dump($i);
int(1)

Thats really all you need. But if you try doing the same thing with an object:

class Person
{
  public $name = 'Alex Super Tramp';
  public $age = 100;
  private $property = 'property';
}
// debugging
php > $p = new Person;
php > var_dump($p);
class Person#1 (3) {
  public $name =>
  string(16) "Alex Super Tramp"
  public $age =>
  int(100)
  private $property =>
  string(8) "property"
}

You get pretty verbose output on that object. For simple objects, this might not be so bad, but the problem is compounded when you are trying to debug a Table class, or a Controller etc. Fortunately, in CakePHP 3 we take advantage of a special magic method, __debugInfo().

Magic Methods to the rescue

Since PHP 5.6, you can add the method __debugInfo() to any class. When instances of said class are passed through var_dump(), PHP will automatically use the array returned by this method to display debug info about that instance.

If the method is omitted, PHP will fallback to outputting all properties in that instance. Here is a lovely example of this in action.

class Person
{
  public $name = 'Alex Super Tramp';
  public $age = 100;
  private $property = 'property';
  public function __debugInfo()
  {
    return ['name' => $this->name];
  }
}
// debugging
php > $p = new Person;
php > var_dump($p);
object Person#1 (1) {
  ["name"] =>
  string(16) "Alex Super Tramp"
}

Fancy, right? Remember, while CakePHP does support this feature automatically in 5.6, users of older PHP versions will fallback to the old, yucky data dump.

How this affects you

There are a few places where __debugInfo() has been useful:

• Form instances output metadata about the schema, errors, and validation rules.
• ResultSet instances output the query that is executed.
• Cell objects will output the environment in which they were created (view layer as well as the current request/response objects).
• Entities will output a plethora of data regarding the current state of the entity. Useful for seeing if the entity is new or has been changed.

You’re also quite welcome to add your own __debugInfo() methods to custom classes. For those of you who are curious, I definitely recommend looking at the list of PHP Magic Methods, which might just be handy ² in a pinch!

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