When using the PCRE functions, it is required that the pattern is enclosed by delimiters. A delimiter can be any non-alphanumeric, non-backslash, non-whitespace character. Leading whitespace before a valid delimiter is silently ignored.
Often used delimiters are forward slashes (/), hash
signs (#) and tildes (~). The
following are all examples of valid delimited patterns.
/foo bar/ #^[^0-9]$# +php+ %[a-zA-Z0-9_-]%
It is also possible to use
bracket style delimiters where the opening and closing brackets are the
starting and ending delimiter, respectively. (),
{}, [] and <>
are all valid bracket style delimiter pairs.
(this [is] a (pattern))
{this [is] a (pattern)}
[this [is] a (pattern)]
<this [is] a (pattern)>
If the delimiter needs to be matched inside the pattern it must be escaped using a backslash. If the delimiter appears often inside the pattern, it is a good idea to choose another delimiter in order to increase readability.
/http:\/\// #http://#
You may add pattern modifiers after the ending delimiter. The following is an example of case-insensitive matching:
#[a-z]#i