Regex help

[dpacmittal]

First of all, sorry for not being able to provide a more appropriate title.

 

Write a function declared as function ReformatPhoneNumber($number), whose argument will contain string data representing some phone number data (entered by the user). A valid phone number may consist of between 7 and 12 digits (0..9). Assume that in between some adjacent digits there may optionally appear either a single space, or a single hyphen (-). Any other phone number should be considered invalid.

 

If the phone number is valid, the return value of your function should contain a string containing between 7 and 12 digits, representing the same phone number after removing all hyphens and spaces. If the phone number is invalid, throw a standard PHP5 Exception initialized with the text "Invalid phone number".

 

The first and the last character of the string should be a number.

 

For example, after calling ReformatPhoneNumber('012-345 69') the return value should be '01234569'. Calling the function with any of these values: '012345', '-012345 678', '01203- 34566', '123456678875432', '1234x567' should result in an exception.

This is a question from elance coding test. I completed it last time by using all sorts of functions and a very basic regex. This time I tried to become brave and thought of solving it completely using Regexes. However I got stuck at multiple points (hence, the inappropriate title).

 

I tried these which are obviously wrong:

if(preg_match('!^\d([\d]+(\s|\-)?){5,10}\d$!',$number))

I know it would accept any length of string.

if(preg_match('!^\d(\d|\s|\-){5,10}\d$!',$number))

This would allow multiple spaces and hyphens next to each other.

 

Normally, my knowledge on regex usually gets me through my work and I don't usually need help in this regard. However, this one completely got me.

Any help would be appreciated.

 

Thanks!

[dpacmittal]

UPDATE:

I tried this new regex. It seems to be working fine except that it is accepting phone numbers with lesser digits. Here is it:

if(preg_match('!^\d(\d|(?<=\d)(\s|\-)?){5,10}\d$!',$number))

[Adam]

function ReformatPhoneNumber($number)
{
    if (preg_match('/^(\d[ -]?){7,12}$/', $number, $matches))
    {
        return preg_replace('/[ -]/', '', $number);
    }

    throw new Exception('Invalid phone number');
}

[Adam]

Actually you may want to use:

 

/^(\d[ -]?){7,12}[^ -]$/

 

This will prevent the last digit being a space or hyphen.

[dpacmittal]

Actually you may want to use:

 

/^(\d[ -]?){7,12}[^ -]$/

 

This will prevent the last digit being a space or hyphen.

Thanks a lot. I was just over-complicating stuff. It was straighforward.

Thanks, again.

[Adam]

No probs