Validar CUIT (Argentina)

function validarCUIT($cuit) {if (strlen($cuit)<11) return false ;$cadena = str_split($cuit);$result = $cadena[0]*5;$result += $cadena[1]*4;$result += $cadena[2]*3;$result += $cadena[3]*2;$result += $cadena[4]*7;$result += $cadena[5]*6;$result += $cadena[6]*5;$result += $cadena[7]*4;$result += $cadena[8]*3;$result += $cadena[9]*2;$div = intval($result/11);$resto = $result - ($div*11);if($resto==0){if($resto==$cadena[10]){return true;}else{return false;}}elseif($resto==1){if($cadena[10]==9 AND $cadena[0]==2 AND $cadena[1]==3){return true;}elseif($cadena[10]==4 AND $cadena[0]==2 AND $cadena[1]==3){return true;}}elseif($cadena[10]==(11-$resto)){return true;}else{return false;}}