A couple days ago, part of the feature that I was working on was to mask the digits in a phone number except for the last 2 digits and leaving the rest of the characters (e.g spaces, dashes, etc.) as is. Since I was working with a PHP project, I knew then that this will have to be done with regex and PHP’s preg_replace() function.
After a few minutes of browsing through regular-expressions.info, I was able to come up with the following regular expression:
/\d(?!\d{0,1}$)/Basically, what this expression means is that after the first delimiter (/) there is a \d which matches all the digits in a string. However, it is followed by a expression group containing regex’s negative lookahead assertion ?!, \d{0,1} which matches to 2 digits, and the end of string character $. This grouping should mean not to match, through the negative lookahead, the 2 digits before the end of the string.
The following is a sample code using this expression and PHP’s preg_replace():
And this results in $maskedPhoneNumber assigned with the string:
(***) ***-**67
Source:
