# 22. Virtuoso Functions Guide - http_value

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## http_value

write to HTTP client or string output stream with HTML escapes
http_value (in val_exprany, [in tag varchar], [in stream any]);
Parameters
val_expr – A value expression. May be any string expression. If val_expr is an XML entity, a serialization of the entity is written to the stream. This is not the string value of the XML fragment, but a serialization of the XML fragment as text including all the markup, i.e. elements, attributes, namespaces, text nodes, etc. To get the string value of an XML entity, convert it to a varchat using cast. Casting as varchar will only produce a concatenation of the text nodes in the XML fragment, leaving out elements, attributes, name spaces, etc.
tag – Optional. If present and is a string, the output will be enclosed in tags named as the string content of tag. If the expression evaluates to 0 or null, it will be ignored.
stream – Optional parameter. If omitted or is 0 and the function is executed within a VSP context, the val_expr will be written to the HTTP client. If present and non-zero, val_expr will be written to the specified stream. If non-zero, the value must be a valid stream obtained from function string_output
Return Values

None

Description

The http_value is used to write to an HTTP client (when in a VSP context) or a specified string output stream. http_value uses HTML-escapes for characters that should be escaped according to the HTML spec.

Errors

SQLSTATE | Error Code | Error Text | Description
--- | --- | --- | ---
37000 | HT006 | http output function outside of http context and no stream specified: %s | occurs if called outside VSP and no string session is given
22023 | SR066 | Unsupported case in CONVERT (<data_type_of 1st arg> -> VARCHAR): %s | if the value passed as the 1st argument can't be converted to a VARCHAR value and it's not a XML/XQUERY tree

Using http_value()
HTTP output

Output of various flavours of http. See string_output and string_output_string for examples how to use http to write to streams other than the HTTP output.

    http (' % <b>')     ' <b>
    http_value (' % <b>')   % &lt;b&gt;
    http_url (' % <b>')  +%25+<b>
    http_value (12, 'li')  <li>12</li>

See Also

http, http_url, string_output, http_rewrite.