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* HTML API: WP_HTML_Span class
* Core class used by the HTML tag processor to represent a textual span
* inside an HTML document.
* This is a two-tuple in disguise, used to avoid the memory overhead
* involved in using an array for the same purpose.
* This class is for internal usage of the WP_HTML_Tag_Processor class.
* @since 6.5.0 Replaced `end` with `length` to more closely align with `substr()`.
* @see WP_HTML_Tag_Processor
* Byte offset into document where span begins.
* Byte length of this span.
* @param int $start Byte offset into document where replacement span begins.
* @param int $length Byte length of span.
public function __construct( $start, $length ) {