is_declared_content_ns example

$with_prefix = $this->ns_to_prefix($key, true);
                $attrs_prefix[$with_prefix[1]] = $this->xml_escape($value);
            }

            $attrs_str = join(' ', array_map($this->map_attrs_func, array_keys($attrs_prefix), array_values($attrs_prefix)));
            if(strlen($attrs_str) > 0) {
                $attrs_str = " " . $attrs_str;
            }

            $with_prefix = $this->ns_to_prefix($name);

            if(!$this->is_declared_content_ns($with_prefix[0])) {
                array_push($this->content_ns_decls, $with_prefix[0]);
            }

            $xmlns_str = '';
            if(count($this->content_ns_decls) > 0) {
                array_unshift($this->content_ns_contexts, $this->content_ns_decls);
                $xmlns_str .= join(' ', array_map($this->map_xmlns_func, array_keys($this->content_ns_contexts[0]), array_values($this->content_ns_contexts[0])));
                if(strlen($xmlns_str) > 0) {
                    $xmlns_str = " " . $xmlns_str;
                }
            }