Yes yes, but when?

How many times did you see methods like prepareXXX() ?

private function prepareArrayToInsertInBd(array $rows) {

    $prepared_rows = array();

    foreach($rows as $row) {
        
        $prepared_row = array();

        $prepared_row['id_row'] = $row['id'];
        $prepared_row['title'] = trim($row['post_title']);
        
        /* more stuff */

        $prepared_rows[] = $prepared_row;
    }

    return $prepared_rows;
}

Should I replace all methods like the previous one?

• Is the method calling to another auxiliar method?
• The "prepare" code can be used in another site?

Lazy load data

public function getPostsData() {
    /* ... some stuff */
    $authors_cached_data = array();

    foreach ($posts_data as &$post) {
        $author_id = $post['author_id']

        // Avoid request already requested author data.
        if (!isset($authors_cached_data[$author_id])) {
            $authors_cached_data[$author_id] = ApiCaller::getData( ... );
        }

        $post['author_data'] = $authors_cached_data[$author_id];
    }

    return $posts_data;
}

What if the method caller does not traverse the entire collection?

We just made unnecessary api calls...

Reducing CCN

$array = array(
	array('pear', 'apple'),
	array('banana', 'coconut'),
	'orange' // This is not an array element
);


foreach ($array as $value) {	
    // Check type of element...
    if (is_array($value)) {
        foreach ($value as $fruit) {
            echo $fruit . PHP_EOL;
        }
    } else {
        echo $value . PHP_EOL;
    }
}

/* OUTPUT:
pear
apple
banana
coconut
orange
*/

Next code do the same

$iterator = new RecursiveArrayIterator($array);

foreach(new RecursiveIteratorIterator($iterator) as $value) {
    echo $value . PHP_EOL;
}

RecursiveIteratorIterator is a decorator that does the check if the element is an array for us.

But, be careful with objects

$object = new stdClass();
$object->property1 = 'property 1';
$object->property2 = 'property 2';

$array = array(
    array('pear', 'apple'),
    array('banana', 'coconut'),
    'orange', // This is not an array element
    $object
);

$iterator = new RecursiveArrayIterator($array);

foreach(new RecursiveIteratorIterator($iterator) as $value) {
    echo $value . PHP_EOL;
}

/* OUTPUT: http://3v4l.org/RNKd1
pear
apple
banana
coconut
orange
property 1
property 2
*/

PHP can iterate the public properties of the objects by default

Avoid confusing method declarations

/**
 *
 * @include_author_data boolean If true, the posts data will 
 *                              include the author data.
 * @return array
 */
public function getPostsData($include_author_data = true) {
    /* ... some stuff */
    if ($include_author_data) {
        foreach ($posts_data as &$post) {
            $author_id = $post['author_id']
            $post['author_data'] = ApiCaller::getData( ... );
        }
    }

    return $posts_data;
}

Example:

$object->getPostsData(false);

//WTF is false? you have to enter to the method to know...

We can do:

PostsDataIterator implements IteratorAggregate {

    protected $collection;

    public function __construct() {
        $collection = $this->getPostsData();
    }

    protected function getPostsData() {
        /* query code ... etc */
        return $posts;
    }

    public function getInnerIterator() {
        return new ArrayIterator($this->collection);
    }
}

PostsDataWithAuthor extends PostsDataIterator {
    
    protected function getPostsData() {
        foreach (parent::getPostsData() as &$post) {
            /* get author data... */
        }
    
        return $posts;
    }
}

Some examples

FilterIterator

Provides a simply interface to implements complex filter rules

abstract FilterIterator extends IteratorIterator implements OuterIterator {
/* Métodos */
public abstract bool accept ( void )
public __construct ( Iterator $iterator )
public mixed current ( void )
public Iterator getInnerIterator ( void )
public mixed key ( void )
public void next ( void )
public void rewind ( void )
public bool valid ( void )
}

DirectoryIterator

<?php

// avoid the use of the PHP native functions in procedural style.

foreach (new DirectoryIterator('/secret_folder/porn') as $fileInfo) {
    if($fileInfo->isDot()) continue;
    echo $fileInfo->getFilename() . "<br>\n";
}

GlobIterator 

// similar to glob PHP function

foreach (new \GlobIterator("*.php") as $php_file) {
    echo "$php_file\n";
}

AppendIterator

<?php

$iterator1 = new ArrayIterator(array(1,2));
$iterator2 = new ArrayIterator(array(3,4));

$appendIterator = new AppendIterator();
$appendIterator->append($iterator1);
$appendIterator->append($iterator2);

foreach($appendIterator as $element) {
	echo $element . PHP_EOL;
}

/*OUTPUT
1
2
3
4
*/

Using nested iterators

<?php

$fruits = new ArrayIterator(array(
    'apple',
    'banana',
    'cherry',
    'orange',
    'pear'
));

// Passing by the custom iterator only a substet of the elements
foreach (new MyCustomIterator(new LimitIterator($fruits , 2, 2)) as $fruit) {
    var_dump($fruit);
}