IF anyone interested to do a simple phone number validation with country code + plus length validation. you may use this validation
anyone has a better suggestion, feel free to share and comment.
AND(LEFT([_THIS],1)="+",LEN([_THIS])>11)
further enhancement on the validation if user accidentally insert โ-โ and " " (space)
example+ 6012-3456 6789
here is the validation formula
AND(LEFT([_THIS],1)="+",LEN([_THIS])>11,NOT(CONTAINS([_THIS],"-")),NOT(CONTAINS([_THIS]," ")))