(PHP 5, PHP 7)
DOMAttr::isId — Checks if attribute is a defined ID
This function checks if the attribute is a defined ID.
According to the DOM standard this requires a DTD which defines the attribute ID to be of type ID. You need to validate your document with DOMDocument::validate or DOMDocument::validateOnParse before using this function.
成功时返回 TRUE， 或者在失败时返回 FALSE。
Example #1 DOMAttr::isId() Example
<?php
$doc = new DomDocument;
// We need to validate our document before refering to the id
$doc->validateOnParse = true;
$doc->Load('book.xml');
// We retrieve the attribute named id of the chapter element
$attr = $doc->getElementsByTagName('chapter')->item(0)->getAttributeNode('id');
var_dump($attr->isId()); // bool(true)
?>