正则表达式匹配从数字2开始的8个字母数字，并且至少有两个数字

Question

Currently I have the following regular expression that matches 8 digits alphanumeric, I want to modify it such that it has to start with the number 2 and contains at least 2 numbers in this 8 digit. How can I do so?

preg_match('/[A-Za-z0-9]{8}/', $bio)

Answer 1

How about:

/^(?=2.*\d)[a-zA-Z0-9]{8}$/

if the number 2 counts for one of the 2 required number.

/^(?=2.*\d.*\d)[a-zA-Z0-9]{8}$/

if the number 2 doesn't count for one of the 2 required number.

explanation:

The regular expression:

(?-imsx:^(?=2.*\d)[a-zA-Z0-9]{8}$)

matches as follows:

NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching 
) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  ^                        the beginning of the string
----------------------------------------------------------------------
  (?=                      look ahead to see if there is:
----------------------------------------------------------------------
    2                        '2'
----------------------------------------------------------------------
    .*                       any character except 
 (0 or more times
                             (matching the most amount possible))
----------------------------------------------------------------------
    \d                       digits (0-9)
----------------------------------------------------------------------
  )                        end of look-ahead
----------------------------------------------------------------------
  [a-zA-Z0-9]{8}           any character of: 'a' to 'z', 'A' to 'Z',
                           '0' to '9' (8 times)
----------------------------------------------------------------------
  $                        before an optional 
, and the end of the
                           string
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------