How could I replace a substring with a variable?

Question

I have a string in the following format:

$string = 'I am {{[1,100]}}'

How could I add to this and replace instances of {{[x,y]}} with a random integer between those values?

In the example provided, the string would become:

$string = 'I am 47'

Answer 1

Use preg_replace_callback() . This uses a function to compute the replacement from the matched part of the input. The function can use rand() to return a random number in the given range, which come from the capture groups in the regexp.

$string = preg_replace_callback('/\{\{\[(\d+),(\d+)\]\}\}/', function($matches) {
    return rand($matches[1], $matches[2]);
}, $string);