14.3.2. Access Request Information
Request information, resulting from an HTTP POST, is available via
the params vector. The params vector is
always available for the purpose in a VSP context. Similarly the
lines and path
vectors are available for the HTTP headers and URL path
respectively.
Parameters stored in the params vector are stored in keyword-value
pairs, such that keywords are stored in the even elements, values
in the odd numbered elements. Vectors and arrays can be accessed
using the aref() and
aset() functions, however, the exact position
of parameters is seldom known. The
get_keyword() function can be used to return
the value of a given parameter. You can specify a default value to
return in case the parameter you are looking for is not found.
get_keyword
(
'param_name',vector[,opt_default_value']);
If a default value other than '' (empty-string) is not required then a short-hand can be used instead.
{?'param_name'}
is equivalent to get_keyword
(
'param_name','params');
Since get_keyword() returns only strings, you
will find that
cast
ing or conversion functions such as atoi()
are very useful here.
Example 14.8. Reading the params Vector
Consider retrieving the following page by means of the URL:
http://myvirtuoso/test.vsp?arg1=1&arg2=test
<html>
<body>
<h1>Test Params</h1>
<?vsp
declare _arg1 integer; -- the underscore helps to differentiate from
declare _arg2 varchar; -- the keyword name, whereas the variable names
declare _arg3 varchar; -- help use remember which is which.
_arg1 := atoi(get_keyword('arg1', params));
_arg2 := {?'arg2'};
_arg3 := get_keyword('arg3', params, 'was empty'};
?>
<p>values returned:</p>
<p>arg1: <?=_arg1?></p>
<p>arg2: <?=_arg2?></p>
<p>arg3: <?=_arg3?></p>
</body>
</html>
![[Tip]](images/tip.png)
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See Also: |
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![[Note]](images/note.png)
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Note: |
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Sometimes a POST can supply a large amount of data, such as from an <INPUT type="file">. When the length of the parameter data exceeds 5,000,000 octets the result is stored as a string session in the params array. In these cases the value should not be copied or converted to a string, it is likely to be truncated. The value should be stored as a BLOB or an external file. When processing possibly large input fields in a form either the fourth parameter to
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