The main class in OpenCReports is called OpenCReport. (Note that the project name is used as singular.)

class OpenCReport {
    public const RESULT_ERROR;
    public const RESULT_STRING;
    public const RESULT_NUMBER;
    public const RESULT_DATETIME;

    public const VARIABLE_EXPRESSION;
    public const VARIABLE_COUNT;
    public const VARIABLE_COUNTALL;
    public const VARIABLE_SUM;
    public const VARIABLE_AVERAGE;
    public const VARIABLE_AVERAGEALL;
    public const VARIABLE_LOWEST;
    public const VARIABLE_HIGHEST;

    public final __construct();

    public final parse_xml(string $filename): bool;
    public final parse_xml_from_buffer(string $buffer): bool;

    public const OUTPUT_PDF;
    public const OUTPUT_HTML;
    public const OUTPUT_TXT;
    public const OUTPUT_CSV;
    public const OUTPUT_XML;
    public const OUTPUT_JSON;
    public final set_output_format(long $format): void;
    public final get_output_format(): long;
    public static final get_output_format_name(long $format):
                     string;

    public final set_output_parameter(
                     string $param,
                     string $value): void;

    public final execute(): bool;
    public final spool(): void;
    public final get_output(): string|false;
    public final get_content_type(): array|false;

    public static final version(): string;

    public final set_numeric_precision_bits(
                     string $expr_string): void;
    public final get_numeric_precision_bits(): long;
    public final set_rounding_mode(
                     string $expr_string): void;

    public final bindtextdomain(
                     string $domainname,
                     string $dirname): void;
    public final set_locale(string $locale): void;

    public final datasource_add(string $source_name,
                                string $source_type,
                                ?array $conn_params = null):
                     ?OpenCReport\Datasource;

    public final datasource_get(string $source_name):
                     ?OpenCReport\Datasource;
    public final query_get(string $query_name):
                     ?OpenCReport\Query;

    public final query_refresh(): void;

    public final expr_parse(string $expr_string):
                     ?OpenCReport\Expr;
    public final expr_error(): ?string;

    public final part_new(): OpenCReport\Part;
    public final part_get_next(): OpenCReport\Part;

    public final function_add(
                     string $expr_func_name,
                     string $zend_func_name,
                     long $n_ops,
                     bool $commutative,
                     bool $associative,
                     bool $left_associative,
                     bool $dont_optimize): bool;

    public final add_precalculation_done_cb(
                     string $callback): void;
    public final add_part_added_cb(
                     string $callback): void;
    public final add_report_added_cb(
                     string $callback): void;

    public final env_get(string $var_name):
                     OpenCReport\Result;

    public final result_new():
                     OpenCReport\Result;

    public final set_mvariable(
                     string $name,
                     ?string $value = null): void;

    public final add_search_path(
                     string $path): void;
    public static final canonicalize_path(
                     string $path): string;
    public final find_file(string $path): $string;

    public static final get_color(
                     string $color_name,
                     ?bool $bgcolor = false): array;

    public final set_paper(string $paper): void;

    public final set_size_unit(string $expr_string):
                     ?OpenCReport\Expr;
    public final get_size_unit():
                     ?OpenCReport\Expr;
    public final set_noquery_show_nodata(
                     string $expr_string):
                     ?OpenCReport\Expr;
    public final get_noquery_show_nodata():
                     ?OpenCReport\Expr;
    public final set_report_height_after_last(
                     string $expr_string):
                     ?OpenCReport\Expr;
    public final get_report_height_after_last():
                     ?OpenCReport\Expr;
    public final set_follower_match_single(
                     string $expr_string):
                     ?OpenCReport\Expr;
    public final get_follower_match_single():
                     ?OpenCReport\Expr;
    public final set_follower_match_single_direct(
                     bool $value): void;
    public final get_follower_match_single_direct()
                     bool;
}