wp-includes/class-wp-block-processor.php:1581Indicates if the matched delimiter is an opening or void delimiter of the given type, if a type is provided, otherwise if it opens any block or implicit freeform HTML content.
$block_typestring[]bool public function opens_block( string ...$block_type ): bool { // HTML spans only open implicit freeform content at the top level. if ( self::HTML_SPAN === $this->state && 1 !== count( $this->open_blocks_at ) ) { return false; } /* * Because HTML spans are discovered after the next delimiter is found, * the delimiter type when visiting HTML spans refers to the type of the * following delimiter. Therefore the HTML case is handled by checking * the state and depth of the stack of open block. */ if ( self::CLOSER === $this->type && ! $this->is_html() ) { return false; } if ( count( $block_type ) === 0 ) { return true; } foreach ( $block_type as $block ) { if ( $this->is_block_type( $block ) ) { return true; } } return false; }Introduced in 6.9.0. Unchanged from 6.9.7 through 7.1.0.
Signature, return type and hooks compared across 3 parsed releases.
src/wp-includes/class-wp-block-processor.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.