PHP RegExp Variable in Function - php

Question

I'm using a Function to parse UBBC and I want to use a function to find data from a database to replace text (a [user] kind of function). However the code is ignoring the RegExp Variable. Is there any way I can get it to recognise the RegExp variable?
PHP Function:
function parse_ubbc($string){
$string = $string;
$tags = array(
"user" => "#\[user\](.*?)\[/user\]#is"
);
$html = array(
"user" => user_to_display("$1", 0)
);
return preg_replace($tags, $html, $string);
}
My function uses the username of the user to get their display name, 0 denotes that it is the username being used and can be ignored for the sake of this.
Any help would be greatly appreciated.

Answer 1

You either rewrite your code to use preg_replace_callback, as advised.
Or your rewrite the regex to use the #e flag:
function parse_ubbc($string){
$string = $string;
$tags = array(
"user" => "#\[user\](.*?)\[/user\]#ise"
);
$html = array(
"user" => 'user_to_display("$1", 0)'
);
return preg_replace($tags, $html, $string);
}
For that it's important that PHP does not execute the function in the replacement array immediately. That's why you have to put the function call into 'user_to_display("$1", 0)' single quotes. So preg_replace executes it later with the #e flag.
A significant gotcha here is, that the username may never contain " double quotes which would allow the regex placeholder $0 to break up the evaluated function call (cause havoc). Hencewhy you have to rewrite the regex itself to use \w+ instead of .*?. Or again just use preg_replace_callback for safety.

Answer 2

You need to use preg_replace_callback if you want to source replacements from a database.

Answer 3

function parse_ubbc($string){
$string = $string;
function get_user_to_display($m){
user_to_display($m[1], 0);
}
return preg_replace_callback('#\[user\](.*?)\[/user\]#is', 'get_user_to_display', $string);
}

Answer 4

You're calling user_to_display() with the string '$1', not the actual found string. Try:
function parse_ubbc($string){
$string = $string;
$tags = array(
"user" => "#\[user\](.*?)\[/user\]#ise"
);
$html = array(
"user" => 'user_to_display("$1", 0)'
);
return preg_replace($tags, $html, $string);
}
The changes are adding 'e' to the end of the regexp string, and putting the function call in quotes.