CODEWITHSUNDEEP
regex
william
william

Reputation: 33

Regular expression model

Hey guys am new to regular expression i have found a regular expression like this ..

preg_match("/^(1[-\s.])?(\()?\d{3}(?(2)\))[-\s.]?\d{3}[-\s.]?\d{4}$/",$number)


preg_match("/^

        (1[-\s.])?  # optional '1-', '1.' or '1'
        ( \( )?     # optional opening parenthesis
        \d{3}       # the area code
        (?(2) \) )  # if there was opening parenthesis, close it
        [-\s.]?     # followed by '-' or '.' or space
        \d{3}       # first 3 digits
        [-\s.]?     # followed by '-' or '.' or space
        \d{4}       # last 4 digits

        $/x",$number);

I found these explanation from a tutorial website ..I just need to know why (?(2)) is assigned here..why questionmark(optional symbol) is applied at the beginning and what is the use of (2) there in that code ..

Am sorry if this question is of low standard since am a newbie .Any help would be appreciated .ThANKS .:)

Upvotes: 0

Views: 49

Answers (1)

ydaetskcoR
ydaetskcoR

Reputation: 56947

The (?(2)\)) is an if clause that checks to see if the 2nd match group was captured.

You should be able to see a break down of your regex at Regex101. It's pretty useful to see what the regex is doing at all points and it's easy to tweak a regex from there.

Upvotes: 1

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