PHP Macros

php_macros.php

<?php
// TODO: bind macroed function to original function's scope

function getFunctionCode($rfn) {
  return implode(array_slice(
    preg_split('/\r?\n/', file_get_contents($rfn->getFileName())),
    $rfn->getStartLine() - 1,
    $rfn->getEndLine() - $rfn->getStartLine() + 1
  ));
}

function createClass($class, $args) {
  $ref_class = new ReflectionClass($class);
  return $ref_class->newInstanceArgs($args);
}

function evalValue($code) {
  eval('$val = ' . $code . ';');
  return $val;
}

function macro($fn, $rewrite) {
  return evalValue(
    $rewrite(
      preg_replace(
        '/^.*function[^(]+/',
        '$myfn = function',
        getFunctionCode(
          createClass(
            'ReflectionFunction',
            array($fn))))));
}

// Testing
$a = 'outer';
$myfunction = function () {
  echo "Outer Hello!\n";
  $a = 'inner';
  return function () use ($a) {
    echo "Inner Hello:" . $a . "\n";
  };
};

$before = $myfunction();
$before();

$wee = macro($before, function ($fn) {
  return str_replace('Hello', 'Hello World', $fn);
});

echo "Macroed!\n";

$wee();