PHP string interpolation.

stringinterpolation.php

<?php

class Message
{
    /**
     * @param  string $message String template
     * @param  array  $context Context providing vars
     * @param  bool   $consume If true, missing matches will be
     *                         removed, else they are left.
     * @return string
     */
    public static function interpolate($message, array $context = array(), $consume = FALSE)
    {
        $getMatchReplace = function($match, $context) use($consume){
            $alt = $consume ? "" : "{".$match."}";
            $out = array_key_exists($match, $context) ? $context[$match] : $alt;
            return is_callable($out) ? call_user_func($out, $match, $context) : $out;
        };

        $replace = array();
        preg_match_all('/\{([^}]+)}/', $message, $matches);

        foreach($matches[1] as $match) {
            $match = trim($match);
            $replace["{".$match."}"] = $getMatchReplace($match, $context);
        }
        //mb_strstr
        return strtr($message, $replace);
    }
}