PHP RegEx - 没有结束分隔符？ [重复]

Question

This question already has an answer here:

• PHP regular expressions: No ending delimiter '^' found in 3 answers

I am fairly new to RegEx and felt I somewhat got the hang of the basics when I was working with my .htaccess file. I am currently working on some form validation to check that the user inputs a valid serial number to the system. The system can accept the following serial format.

• I-SERIAL-123
• I-SERIAL123
• SERIAL-123
• SERIAL123

I am using the preg_match function to check whether this expression is satisfied, if so the field is submitted.

Current Expression

if (preg_match("^[A-Z0-9\-]{5}$", $_GET['serial']) === false) 

However PHP keeps throwing an "No ending delimiter found" exception, I've looked at a couple of PHP cheat sheets and I don't see any immediate issues in my syntax.

Any pointers would be greatly appreciated, thanks.

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Answer 1

You need delimiters around your regex, usually /s:

if (preg_match("/^[A-Z0-9\-]{5}$/", $_GET['serial']) === false)
                ^---------------^

But any non-alphanumeric character is valid (even paired brackets), although it makes most sense to use ~, # or other symbols that aren't regex metacharacters or often used in text searches:

if (preg_match("#^[A-Z0-9\-]{5}$#", $_GET['serial']) === false)

In your case, as pointed out by Andy Lester, the regex engine thinks that ^ was supposed to be the delimiter (possible, but you then lose the "start of string" anchor for use in your regex and have to use \A instead):

if (preg_match("^\A[A-Z0-9\-]{5}$^", $_GET['serial']) === false)