Can explain this block Code to me PHP XML DOMDocument Syntax - php

Question

I am currently learning different ways to iterate through the xml document tags using the
php DOMDocument object, I understand the foreach loop for iterating through the tags, but the $element->item(0)->childNodes->item(0)->nodeValue is a bit unclear to me could somebody explain to me in detail? Thank you.
<?php
$xmlDoc = new DOMDocument();
$xmlDoc->load('StudentData.xml');
$studentRoot = $xmlDoc->getElementsByTagName('Student');
for ($i = 0; $i < ($studentRoot->length); $i++) {
$firstNameTags = $studentRoot->item($i)->getElementsByTagName('FirstName');
echo $firstNameTags->item(0)->childNodes->item(0)->nodeValue.' <br />';
}
/* so much easier and clear to understand! */
foreach($studentRoot as $node) {
/* For every <student> Tag as a separate node,
step into it's child node, and for each child,
echo the text content inside */
foreach($node->childNodes as $child) {
echo $child->textContent.'<br />';
}
}
?>

Answer 1

$elements->item(0)->childNodes->item(0)->nodeValue
First:
$elements
The current elements$ as parsed and referenced. In the code example, that would be:
$firstNameTags = $studentRoot->item($i)->getElementsByTagName('FirstName');
$firstNameTags->...
Next:
->item(0)
Get a reference to the first of the $elements item in the node list. Since this is zero-indexed, ->item(0) would get the first node in the list by index.
->childNodes
Get a list of the child nodes to that first $elements node referenced by ->item(0) above. As there is no (), this is a (read only) property of the DOMNodeList.
->item(0)
Again, get the first node in the list of child nodes by index.
->nodeValue
The value of the node itself.
If the form of the state alone:
$obj->method()->method()->prop
Confuses you, look into method chaining, which is what this uses to put all of those method calls together.
$ Note, you left off the s, but that indicates there's one or more possible by convention. So $element would be zero or one element reference, $elements might be zero, one or more in a collection of $element.