PHP FilterIterator::next() Method: Usage and Examples

The PHP FilterIterator::next API performs a focused operation on an object or value. The examples below show its effect on actual data.

Advances to the next iteration position; an exhausted iterator has no current entry.

What Is FilterIterator::next in PHP?

Advances to the next iteration position; an exhausted iterator has no current entry.

Syntax:

FilterIterator::next()

This operation has no parameters.

Return type declared by PHP: mixed / not explicitly declared. The value or side effect is demonstrated in the examples below.

Example 1: Basic Usage

This example uses a small input to make the main behavior visible.

<?php

class MinimumFilter extends FilterIterator {
    public function accept(): bool { return $this->current() >= 10; }
}
$filterIterator = new MinimumFilter(new ArrayIterator([3, 10, 12, 15]));
$filterIterator->rewind();
$filterIterator->next();
var_dump($filterIterator->current());

Output:

int(12)

Advances to the next iteration position; an exhausted iterator has no current entry.

Example 2: A Different Input

A different set of values shows the same operation in another situation.

<?php

class MinimumFilter extends FilterIterator {
    public function accept(): bool { return $this->current() >= 11; }
}
$filterIterator = new MinimumFilter(new ArrayIterator([1, 5, 11, 18]));
$filterIterator->rewind();
$filterIterator->next();
var_dump($filterIterator->current());

Output:

int(18)

The predicate should be inexpensive and free of side effects, because iteration can call accept() repeatedly.

Practical Example: Applying the Feature

This example shows an application-style use of the feature, with its surrounding setup visible.

<?php

class MinimumFilter extends FilterIterator {
    public function accept(): bool { return $this->current() >= 20; }
}
$filterIterator = new MinimumFilter(new ArrayIterator([0, 20, 30, 40]));
$filterIterator->rewind();
$filterIterator->next();
var_dump($filterIterator->current());

Output:

int(30)

The code is shown for learning. Adjust the class names, inputs and error handling to suit your application.

Important Behavior and Edge Cases

• The predicate should be inexpensive and free of side effects, because iteration can call accept() repeatedly.
• Advances to the next iteration position; an exhausted iterator has no current entry.
• Observe differences in empty inputs, invalid states and optional extension availability where relevant.

Comparison With Related Approaches

Common Beginner Mistakes

Key Takeaways

• Advances to the next iteration position; an exhausted iterator has no current entry.
• The predicate should be inexpensive and free of side effects, because iteration can call accept() repeatedly.
• Use the example that matches the values, runtime version and dependencies in your application.

FilterIterator::next is useful when its behavior matches the data structure and lifecycle of your PHP application. Choose it with a clear understanding of its preconditions and returned values.