Traversal
A traversal is the process of listing all elements in a data structure.
foreach() is a command to do a traversal on an array, an object or an iterable object. It is also possible to use an iterator.
Traversal may be recursive: for example, the recursive iterators in the SPL library feature the RecursiveArrayIterator class, which traverses multi-dimensional arrays.
Traversal of a tree or graph data structure turns the graph into an array-like list.
<?php
$array = range(0, 9);
foreach($array as $item) {
print "$item\n";
// list digits from 0 to 9
}
// adds 10, 11, 12 to the previous array
// in a separate
$array[] = [10, 11, 12];
$iterator = new RecursiveArrayIterator($array);
foreach($iterator as $item) {
print "$item\n";
// list digits from 0 to 12
}
?>