Parse through a string php and replace substrings

Question

I have a string, in PHP and the string has occurrences of the pattern %%abc%%(some substring)%%xyz%%

There are multiple occurrences of such substrings withi

Answer 1

This is a situation that calls for preg_replace_callback:

// Assume this already exists
function mapSubstringToInteger($str) {
    return (strlen($str) % 4) + 1;
}

// So you can now write this:
$pattern = '/%%abc%%(.*?)%%xyz%%/';
$replacements = array('r1', 'r2', 'r3', 'r4');
$callback = function($matches) use ($replacements) {
    return $replacements[mapSubstringToInteger($matches[1])];
};

preg_replace_callback($pattern, $callback, $input);