URL 정규식 comprension

Question

나는이 정규식을 내가 PHP에서 사용하는 것으로 파악하려고 노력하고있다. 그러나 나는 멍청이 다. 그래서 나에게는 매우 어렵다. 이 정규식은 무엇을 설명해 주시겠습니까? /(?:https?:\/\/)?(?:[a-zA-Z0-9.-]+?\.(?:[a-zA-Z])|\d+\.\d+\.\d+\.\d+)/

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Answer 1

Brackets 

[0-9] - It matches any decimal digit from 0 through 9. 
[a-z] - It matches any character from lower-case a through lowercase z. 
[A-Z] - It matches any character from uppercase A through uppercase Z. 
[a-Z] - It matches any character from lowercase a through uppercase Z. 

Quantifiers 

p+ - It matches any string containing at least one p. 
p* - It matches any string containing zero or more p's.  
p? - It matches any string containing zero or one p's. 
p{N} - It matches any string containing a sequence of N p's  
p{2,3} - It matches any string containing a sequence of two or three p's. 
p{2, } - It matches any string containing a sequence of at least two p's. 
p$ - It matches any string with p at the end of it. 
^p - It matches any string with p at the beginning of it. 

Expression & Description 

[[:alpha:]] - It matches any string containing alphabetic characters aA through zZ. 
[[:digit:]] - It matches any string containing numerical digits 0 through 9. 
[[:alnum:]] - It matches any string containing alphanumeric characters aA through zZ and 0 through 9. 
[[:space:]] - It matches any string containing a space. 

: Regex