Regular expression reverse reference of PHP core technologies and best practices

Regular expression reverse reference of PHP core technologies and best practices Regular expression reverse reference of PHP core technologies and best practices

The reverse reference is used to repeatedly search text matched by a previous group. For example, "\ 1" indicates the text matched by group 1:

\ B (\ w +) \ B \ s + \ 1 \ B

You can use "\ k "Previous example:

\ B (? \ W +) \ B \ s + \ k \ B

[Example]: UBB tag code

UBB labels are used to replace HTML in forums and message boards to achieve some simple HTML effects and prevent HTML security problems from being abused.

In the end, the UBB tag still needs to be parsed into HTML code for the browser to understand. the url tag is used as an example.

Required bytes url1_1.gif [/url]"

 \ D \. gif) \ [\/url \] # ","; Var_dump ($ s);?>