I'm looking at this example array_filter comment and he passes an argument to array_filter as
array_filter($subject, array(new array_ereg("image[0-9]{3}\.png"), 'ereg')
How is it that the callback accepts an array with multiple arguments one of them being the actual callback function
In PHP it is possible to represent a callable using an array in the following format.
array($object, 'methodName')
The documentation itself states:
A method of an instantiated object is passed as an array containing an object at index 0 and the method name at index 1.
It is quite common to see this used with the $this variable inside objects.
In your example, the first element of the array is created with new, and is the instantiated object required, and ereg is the method.
The array_filter functions expects a callable for it's second parameter.
PHP understands an array($instance, 'methodname') as callable for instance methods, and array('classname', 'staticmethodname') for static methods (or simple 'classname::staticmethod' since version 5.2.3 .
To extend other answers. In PHP >= 5.3, we can use closures.
$numbers = range(1,10);
$newNumbers = array_filter($numbers, function($value) {
return ($value & 1) === false;
});
// $newNumbers now contains only even integers. 2, 4, 6, 8, 10.
Have a look at the PHP: Callbacks page.
When an array is specified for a callable parameter, you are specifying an object and a method of that object. For example:
$object = new MyClass();
array_filter($input, array($object, 'myClassMethod'));
In the example you provided:
array_filter($subject, array(new array_ereg("image[0-9]{3}\.png"), 'ereg');
The new instance of array_ereg is the object and ereg is the method of the array_ereg class.
eregfunctions are deprecated, and you should avoid using them.