PHP - Regex : I need help to build regex according these rules

Question

I need help building a regular expression for preg_match according these rules:

1. first and last char- letter/digit only.
2. empty space not allowed
3. char can be only - letter/digit/'-'/'_'/'.'

Legal examples :

1. b.t612_rt
2. rut-be
3. rut7565

Not legal example :

1. .btr78; btr78- (first/last allowed chars)
2. start end; star t end; (any empty space)
3. tr$be; tr*rt; tr/tr ... (not allowed chars)

Edit: I remove 4 rule with neigbor chars '_'\\'-'\\'.'

please help me.

Thanks

Answer 1

Try this regular expression:

^[A-Za-z0-9]+([-_.][A-Za-z0-9]+)*$

This matches any sequence that starts with at least one letter or digit ( ^[A-Za-z0-9]+ ) that may be followed by zero or more sequences of one of - , _ , or . ( [-_.] ) that must be followed by at least one letter or digit ( [A-Za-z0-9]+ ).

Answer 2

Try this:

^[\p{L}\p{N}][\p{L}\p{N}_.-]*[\p{L}\p{N}]$

In PHP:

if (preg_match(
    '%^               # start of string
    [\p{L}\p{N}]      # letter or digit
    [\p{L}\p{N}_.-]*  # any number of letters/digits/-_.
    [\p{L}\p{N}]      # letter or digit
    $                 # end of the string.
    %xu', 
    $subject)) {
    # Successful match
} else {
    # Match attempt failed
}

Minimum string length: Two characters.

Answer 3

Well, for each of your rules:

1. First and last letter/digit:

    ^[a-z0-9] 

   and

    [a-z0-9]$ 

2. empty space not allowed (nothing is needed, since we're doing a positive match and don't allow any whitespace anywhere):

3. Only letters/digits/-/_/.

    [a-z0-9_.-]* 

4. No neighboring symbols:

    (?!.*[_.-][_.-]) 

So, all together:

/^[a-z0-9](?!.*[_.-][_.-])[a-z0-9_.-]*[a-z0-9]$/i

But with all regexes, there are multiple solutions, so try it out...

Edit: for your edit :

/^[a-z0-9][a-z0-9_.-]*[a-z0-9]$/i

You just remove the section for the rule you want to change/remote. it's that easy...

Answer 4

对于提供的示例，这似乎很好用： $patt = '/^[a-zA-Z0-9]+([-._][a-zA-Z0-9]+)*$/';