How to check post parameter value?

Hi Gopi,

optimized your iRule and also removed certain coding glitches for you...

when HTTP_REQUEST {
    if { not ( [IP::addr [IP::remote_addr] equals x.x.0.0/16] ) 
         and ( [HTTP::method] equals "POST" ) 
         and ( [string tolower [HTTP::uri]] equals "/folder/page.php" ) } then {
        if { [HTTP::header value Content-Length] > 0 } then {
            if { [HTTP::header value Content-Length] < 1048576 } then {
                HTTP::collect 1048576
            } else {
                HTTP::collect [HTTP::header Content-Length]
            }
        }
    }
}
when HTTP_REQUEST_DATA { 
    set SSOPayload [string tolower [HTTP::payload]] 
    log local0. "SSOPayload : $SSOPayload" 
     Extract the entire HTTP request body and escape it to become a HTTP::uri string (for easier parsings) 
     Try to parse type value from the HTTP request body.
    if { [catch {
        if { [URI::decode [URI::query "?[HTTP::payload]" type]] ne "abcdefgh" } then {
            HTTP::respond 403 content " FORBIDDEN " "Content-Type" "text/html" "Connection" "close"
            log local0. "Wrong Type : $type"
        } else {
            log local0. "Good Type : $type"
             Let the request pass....
        }
    }] } then {
        log local0. "Failed to parse HTTP::payload for type value"
        HTTP::respond 500 content " FORBIDDEN " "Content-Type" "text/html" "Connection" "close"
    }
}

Note: Did some rework on your yntax to send a HTTP err500 in the case of an exemption.

Note: Also removed certain unnessesary code. Define variables only if required, this will safe you a bunch of CPU cycles...

Cheers, Kai