Optimizing String Placeholder Substitution with RegEx

The function dynStr() aims to search for and replace placeholder variables in a given string, denoted by curly brackets. While it functions correctly, its efficiency and simplicity can be improved.

One key issue with dynStr() lies in its double-array structure for $matches. Using two foreach loops to access the desired data is inefficient. Consider simplifying the regular expression to directly extract the placeholder variable without the need for further processing:

preg_match_all('/{\w }/', $str, $matches);

Next, the loop to replace the placeholder variables can be optimized. The current approach uses several string manipulation operations and array lookups, making it unnecessarily complex:

foreach($match_group as $match) {
    // ...
    $str = ...
}

A simpler and more concise alternative is to use a single function call, substituting the placeholder directly:

foreach($matches[0] as $match) {
    $str = strtr($str, [$match => $vars[strtolower($match)]]);
}

The strtr() function efficiently performs multiple replacements by defining a mapping between the placeholder variables and their corresponding values in the $vars array.

Additionally, the function can be made case-insensitive by converting both the placeholder variables and the array keys to lowercase, eliminating the need for additional processing:

$allowed = array_keys(array_change_key_case($vars, CASE_LOWER));
...
$str = (in_array(strtolower($match), $allowed)) ? str_replace("{".$match_up."}", $vars[strtolower($match)], $str) : str_replace("{".$match_up."}", '', $str);

Incorporating these optimizations results in a more efficient and streamlined dynStr() function:

function dynStr($str,$vars) {
    preg_match_all('/{\w }/', $str, $matches);
    foreach($matches[0] as $match) {
        $vars = array_change_key_case($vars, CASE_LOWER);
        $str = strtr($str, [$match => $vars[strtolower($match)]]);
    }
    return $str;
}