I never see more 5 knotes VRB. This are sources are not official they and based on none official documents. I never see VRB with 4 or 5 knots. It can maybe in most cases if you have wind with 5 knots and its a little variable then you get 260V350 as addition information… So the XML might be well, but it’s not well decoded. If you want to get the best weather information, you need to decode a metar code by yourself. We can say ok max 6 knotes but in real live i never see VRB06.
There is a point more! You can get light wind with 2 knots from a direction. So if you don’t get any informations about VRB in XML file you are not really sure if VRB or not. 
The best is to decode this kind of metar:
METAR EDVE 111920Z VRB02KT 3000 BR FEW001 SCT003 BKN012 M01/M01 Q1025
I can see that temp and dew point is same… If you get this, i can say hey we have fog. And yes the visibility is down to 3km and we have fee clouds with 100ft down and scattered up to 300 ft and broken on 1200ft… Normally this sounds like a CATII approach or CATIII. So category for approaching an airport with low visibility… OK tooooo much information.
My over 10 years aviation experience i never see VRB and higher than 4 knots…
So if you get 0 to 0 the wind is calm.
Soooo… Its your decision to say wind is VRB or not. If you say its VRB it can be wrong if you say 0/3 it can be wrong too… If i must take this decision based on xml data, i will do:
if 0/2 oder 0/3 then VRB all others can be without VRB.
Or you start do decode the real metar code and get exactly this information what you want and what you need.
`function metar_raw_decoder($metartaf){
$do_out = array();
$parts = explode(' ',$metartaf);
$cntdata = count($parts);
for($i=0;$i<$cntdata;$i++){
#get date
if(preg_match('/([0-9]{2})([0-9]{2})([0-9]{2})Z/',$parts[$i],$part)){
$do_out['reptime']['day'] = $part[1];
$do_out['reptime']['hour'] = $part[2];
$do_out['reptime']['min'] = $part[3];
}
#get wind
if(preg_match('/([0-9]{3}|VRB)([0-9]{2,3})G?([0-9]{2,3})?KT/',$parts[$i],$part)){
$do_out['wind']['dir'] = ($part[1]/1);
$do_out['wind']['power'] = ($part[2]/1);
if(isset($part[3])){
$do_out['wind']['gusts'] = ($part[3]/1);
}
}
if(preg_match('/^([0-9]{3})V([0-9]{3})$/',$parts[$i],$part)){
$do_out['wind']['change'] = $part[0];
$do_out['wind']['change_from'] = ($part[1]/1);
$do_out['wind']['change_to'] = ($part[2]/1);
}
#get visibility
if(preg_match('/^[0-9]{4}$/',$parts[$i],$part)){
$do_out['visibility']['base'] = $part[0];
}
if(preg_match('/^([0-9]{4})([A-Z])$/',$parts[$i],$part)){
$do_out['visibility']['distance'] = $part[1];
$do_out['visibility']['direction'] = $part[2];
}
#get clouds '^(VV|FEW|SCT|BKN|OVC)([0-9]{3}|///)(CB|TCU)?$'
if(preg_match('/^(VV|FEW|SCT|BKN|OVC)([0-9]{3}|\/\/\/)(CB|TCU|ACC)?$/',$parts[$i],$part)){
$do_out['cloud']['discription'] = $part[1];
$do_out['cloud']['height'] = $part[2];
if(isset($part[3])){
$do_out['cloud']['special'] = $part[3];
}
}
#get cavok
if(preg_match('/^CAVOK$/',$parts[$i],$part)){
$do_out['CAVOK'] = $part[0];
}
#get cavok
if(preg_match('/^NSC/',$parts[$i],$part)){
$do_out['NSC'] = $part[0];
}
#get temperature
if(preg_match('/^([0-9\-]{2,3})\/([0-9\-]{2,3})$/',$parts[$i],$part)){
$do_out['temp']['norm'] = ($part[1]/1);
$do_out['temp']['dewpoint'] = ($part[2]/1);
}
#get temperature
if(preg_match('/^M([0-9\-]{2,3})\/M([0-9\-]{2,3})$/',$parts[$i],$part)){
$do_out['temp']['norm'] = -($part[1]/1);
$do_out['temp']['dewpoint'] = -($part[2]/1);
}
#get pressure
if(preg_match('/^Q([0-9]{4}$)/',$parts[$i],$part)){
$do_out['pressure'] = $part[1];
}
#get tafdatetime
if(preg_match('/^([0-9\-]{2})([0-9\-]{2})\/([0-9\-]{2})([0-9\-]{2})/',$parts[$i],$part)){
$do_out['taftime']['dat_from'] = $part[1];
$do_out['taftime']['time_from'] = $part[2];
$do_out['taftime']['dat_to'] = $part[3];
$do_out['taftime']['time_to'] = $part[4];
}
#get becoming
if(preg_match('/^BECMG/',$parts[$i],$part)){
$do_out['BECMG'] = $part[0];
}
#get probability
if(preg_match('/^(PROB)([0-9]{2})$/',$parts[$i],$part)){
$do_out['prob']['main'] = $part[1];
$do_out['prob']['chance'] = $part[2];
}
#get temporär
if(preg_match('/^TEMPO$/',$parts[$i],$part)){
$do_out['TEMPO'] = $part[0];
}
#get nosig
if(preg_match('/^NOSIG$/',$parts[$i],$part)){
$do_out['NOSIG'] = $part[0];
}
#weather proximity discriptor precipitation
if($i>3){
if(preg_match('/^([\-\+])?([A-Z]{2})([A-Z]{2})$/',$parts[$i],$part)){
$do_out['pdp']['proximity'] = $part[1];
$do_out['pdp']['discriptor'] = $part[2];
$do_out['pdp']['precipitation'] = $part[3];
}
}
#weather obscuration
if(preg_match('/^([A-Z]{2})$/',$parts[$i],$part)){
$do_out['obscuration'] = $part[0];
}
#cancellation
if(preg_match('/^CNL$/',$parts[$i],$part)){
$do_out['CNL'] = $part[0];
}
}
return $do_out;
}
function abbi($abbi){
switch($abbi){
case "N":
$abbiout = "Norden";
break;
case "E":
$abbiout = "Osten";
break;
case "S":
$abbiout = "Süden";
break;
case "W":
$abbiout = "Westen";
break;
case "BECMG":
$abbiout = "Wetter ändert sich";
break;
case "TEMPO":
$abbiout = "Temporär";
break;
case "PROB":
$abbiout = "Wahrscheinlichkeit:";
break;
case "NOSIG":
$abbiout = "Keine Änderung in den n¨chsten zwei Stunden zu erwarten";
break;
case "CAVOK":
$abbiout = "Wolken und Sicht sind in Ordnung";
break;
case "VRB":
$abbiout = "Variabel";
break;
case "G":
$abbiout = "Bö:en mit bis zu";
break;
case "BR":
$abbiout = "Dunst";
break;
case "FG":
$abbiout = "Nebelig";
break;
case "VC":
$abbiout = "Örtlich";
break;
case "MI":
$abbiout = "flach";
break;
case "PR":
$abbiout = "stellenweise";
break;
case "BC":
$abbiout = "einzelne Schwaden";
break;
case "DR":
$abbiout = "fegend";
break;
case "BL":
$abbiout = "treibender";
break;
case "SH":
$abbiout = "Schauer";
break;
case "RA":
$abbiout = "Regen";
break;
case "TS":
$abbiout = "Gewitter";
break;
case "FZ":
$abbiout = "gefrierender";
break;
case "DZ":
$abbiout = "Sprühregen";
break;
case "SN":
$abbiout = "Schnee";
break;
case "SG":
$abbiout = "Schneegriesel";
break;
case "IC":
$abbiout = "Eisnadeln";
break;
case "PL":
$abbiout = "Eiskörper";
break;
case "GR":
$abbiout = "Hagel";
break;
case "SH":
$abbiout = "Reif/Frostgraupel";
break;
case "UP":
$abbiout = "Unbestimmter Niederschlag";
break;
case "FU":
$abbiout = "Rauch";
break;
case "VA":
$abbiout = "Vulkanasche";
break;
case "DU":
$abbiout = "verbreitet Staub";
break;
case "SA":
$abbiout = "Sand";
break;
case "HZ":
$abbiout = "trockener Dunst";
break;
case "PY":
$abbiout = "Sprühnebel/Gischt";
break;
case "FEW":
$abbiout = "Bedeckung 1 bis 2 Achtel";
break;
case "SCT":
$abbiout = "Bedeckung 3 bis 4 Achtel";
break;
case "BKN":
$abbiout = "Bedeckung 5 bis 7 Achtel";
break;
case "OVC":
$abbiout = "Bedeckt";
break;
case "NSC":
$abbiout = "Wolkenfrei bis 5000ft ca. 3km Höhe";
break;
case "CB":
$abbiout = "Cumulonimbus Wolken";
break;
case "TCU":
$abbiout = "Aufgetürmte Cumulus Wolken";
break;
case "BECMG":
$abbiout = "Wetter ändert sich";
break;
case "CNL":
$abbiout = "Gestrichen";
break;
default:
$abbiout = "Uebersetzung von ".$abbi." fehlt.";
break;
}
return $abbiout;
}
function compass_converter($dir){
switch ($dir){
case 338 <= $dir:
$dirrose = "Nord";
break;
case 293 <= $dir:
$dirrose = "NordWest";
break;
case 248 <= $dir:
$dirrose = "West";
break;
case 203 <= $dir:
$dirrose = "SüdWest";
break;
case 180 <= $dir:
$dirrose = "Süd";
break;
case 113 <= $dir:
$dirrose = "SüdOst";
break;
case 90 <= $dir:
$dirrose = "Ost";
break;
case 23 <= $dir:
$dirrose = "NordOst";
break;
case 0 <= $dir:
$dirrose = "Nord";
break;
}
return $dirrose;
}
function beaufort_converter($wind){
switch ($wind){
case $wind == 1:
$windbf = "0";
break;
case 71 <= $wind:
$windbf = "12";
break;
case 63 <= $wind:
$windbf = "11";
break;
case 55 <= $wind:
$windbf = "10";
break;
case 47 <= $wind:
$windbf = "9";
break;
case 40 <= $wind:
$windbf = "8";
break;
case 33 <= $wind:
$windbf = "7";
break;
case 27 <= $wind:
$windbf = "6";
break;
case 21 <= $wind:
$windbf = "5";
break;
case 15 <= $wind:
$windbf = "4";
break;
case 10 <= $wind:
$windbf = "3";
break;
case 6 <= $wind:
$windbf = "2";
break;
case 3 <= $wind:
$windbf = "1";
break;
}
return $windbf;
}`
Piece code of my decoder. 
