how to validate phonenumber with out using localvariable?

In which variable you stored your data? It will be either local or RI variable.

What is this question about? Is there a specific reason to not use locals?

i want to know both the ways to validate..

could you give me an example for with and without using locals?

Sorry, the validation of a phone number does not depend on using locals in any way.

Please help me to understand your question.

a!localVariables(
  local!phoneNum,
  a!textField(
    label: "Phone Number",
    value: local!phoneNum,
    saveInto: local!phoneNum,
    validations: if(
      regexmatch(
        "[0-9] [0-9]", /*paste your regex here*/
        local!phoneNum /*Put local or ri variable name*/
      ),
      {},
      "Invalid Phone Number"
    )
  )
)

The code to validate for phone number by using local variables. i dont think so we can achieve it without using local or ri variable.

If you are capturing the value, then to store the value, you will need to have a variable. It can be either a Rule input or a local variable. 
If you are trying to validate an existing value, then you can do it without a variable.

Both ways have multiple ways of doing it. 

1. Regex Match
2. Specifying lower and upper bounds of the number (eg. 1111111-9999999)
3. Check the length of the value