The PHP AppendIterator::valid API performs a focused operation on an object or value. The examples below show its effect on actual data.
Reports whether an iterator currently points at a valid entry.
What Is AppendIterator::valid in PHP?
Reports whether an iterator currently points at a valid entry.
Syntax:
AppendIterator::valid()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
$appendIterator = new AppendIterator();
$appendIterator->append(new ArrayIterator(["pear" => 4, "apple" => 2, "plum" => 9]));
$appendIterator->append(new ArrayIterator(["extra" => "included"]));
$appendIterator->rewind();
var_dump($appendIterator->valid());Output:
bool(true)Reports whether an iterator currently points at a valid entry.
Example 2: A Different Input
A different set of values shows the same operation in another situation.
<?php
$appendIterator = new AppendIterator();
$appendIterator->append(new ArrayIterator(["first" => "draft", "second" => "ready", "third" => "done"]));
$appendIterator->append(new ArrayIterator(["extra" => "included"]));
$appendIterator->rewind();
var_dump($appendIterator->valid());Output:
bool(true)The current inner iterator changes when the previous one is exhausted; keys can repeat across appended iterators.
Practical Example: Applying the Feature
This example shows an application-style use of the feature, with its surrounding setup visible.
<?php
$appendIterator = new AppendIterator();
$appendIterator->append(new ArrayIterator([10, 20, 30, 40]));
$appendIterator->append(new ArrayIterator(["extra" => "included"]));
$appendIterator->rewind();
var_dump($appendIterator->valid());Output:
bool(true)The code is shown for learning. Adjust the class names, inputs and error handling to suit your application.
Important Behavior and Edge Cases
- The current inner iterator changes when the previous one is exhausted; keys can repeat across appended iterators.
- Reports whether an iterator currently points at a valid entry.
- Observe differences in empty inputs, invalid states and optional extension availability where relevant.
Comparison With Related Approaches
| Approach | Important Difference |
|---|---|
AppendIterator::valid | Reports whether an iterator currently points at a valid entry. |
| ArrayIterator | ArrayIterator traverses one sequence; AppendIterator chains several iterators into a single traversal. |
Common Beginner Mistakes
| Mistake | Correct Approach |
|---|---|
Ignoring the documented state or precondition of AppendIterator::valid | The current inner iterator changes when the previous one is exhausted; keys can repeat across appended iterators. |
| Expecting a different type of result | Read the declared return type and distinguish returned values from changes to the source object. |
| Assuming a related API works identically | ArrayIterator traverses one sequence; AppendIterator chains several iterators into a single traversal. |
Key Takeaways
- Reports whether an iterator currently points at a valid entry.
- The current inner iterator changes when the previous one is exhausted; keys can repeat across appended iterators.
- Use the example that matches the values, runtime version and dependencies in your application.
AppendIterator::valid 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.