I need a Regex to accept the input only following possible cases like
1.It start with characters only [a-zA-Z]
2.It may contains numbers but it may not repeated 3 or moretimes.
Example:
akjsjdfljsfjl133113 Valid
123123sfsf not valid
asfsdf1111asdf notvalid adf111 not valid
I have tried this code
$input_line="sfjs123232";
preg_match("/^[a-zA-Z](\d)\1{2,}/", $input_line, $output_array);
You can use a Negative Lookahead here.
^[a-zA-Z]+(?:(?!.*(\d)\1{2,}).)*$
See Live demo
Regular expression
^ the beginning of the string
[a-zA-Z]+ any character of: 'a' to 'z', 'A' to 'Z' (1 or more times)
(?: group, but do not capture (0 or more times)
(?! look ahead to see if there is not:
.* any character except \n (0 or more times)
( group and capture to \1:
\d digits (0-9)
) end of \1
\1{2,} what was matched by capture \1 (at least 2 times)
) end of look-ahead
. any character except \n
)* end of grouping
$ before an optional \n, and the end of the string
a121212121212? Your regex matches that. But I probably misunderstood the problem: I thought it was about digits not appearing 3 times anywhere in the string. This is the problem that I don't know how to solve without using infinite lookbehinds (not available in PHP).
akjsjdfljsfjl133113 is a valid string, even though it has 3 1s. +1 :)
abc111def
adf111not valid?repeated three timesmeans that it is present four or more times (the first instance, then the three repeats.) :)a121212121212acceptable? The digits 1 and 2 are repeated many times in the string. If it is acceptable and you only meant not repeated consecutively, then I misunderstood the question.