使用数据库中的值替换字符串中的自定义标记

Question

what I need to do is to parse a string similar to this:

{a}3{/a}*{b}4{/b}

or this

{a}3{/a}/{b}2{/b}*100

I need to substitute in that string those values within the tags with real values from the database, the first example:

SELECT value FROM table WHERE id = 3;

SELECT value FROM table WHERE id = 4;

This function:

preg_replace_callback('/(?>{([^}]+)})(.*)?{\/\1}/sim', 'find_tags_callback', $string);

Actually returns the ids contained in the string, the problem is that I'm stuck there. In pseudo code I would need to:

Extract the first id from the string.

Run my query.

Substitute that id with the correct value.

[Do the same for all tags]

Finish having back the initial string with the correct value inside. The first might be

10*3

the second

40/90*100

Any idea how to do this, I'm completely stuck.

Thanks

Answer 1

Do a database query to get all the values, and put them into an array keyed off the IDs. In the code below, I assume the array is named $tags.

$new_string = preg_replace_callback('/\{([^}]+)\}(.+?)\{/\1\}/sim', 
    function ($match) use ($tags) {
        return $tags[$match[2]];
    }, $string);

The use ($tags) declaration allows the function to reference the external variable $tags.