Process call argument escaping on Windows with PHP

escape_args.php

<?php
/**
 * Escapes a single argument to be glued together and passed into
 * CreateProcess on Windows through `proc_open`.
 *
 * Adapted from https://blogs.msdn.microsoft.com/twistylittlepassagesallalike/2011/04/23/everyone-quotes-command-line-arguments-the-wrong-way/
 *
 * @param  string The argument to be escaped
 * @result string Escaped argument that can be used in a CreateProcess call
 */
function escapeWindowsArgv($value) {
  // Don't quote unless we actually need to do so hopefully
  // avoid problems if programs won't parse quotes properly
  if ($value && !preg_match('/["[:space:]]/', $value)) {
      return $value;
  }

  $result = '"';
  $len = strlen($value);
  for ($i = 0; $i < $len; $i++) {
      $numBackslashes = 0;

      while ($i < $len && $value[$i] == '\\') {
          $i++;
          $numBackslashes++;
      }

      if ($i == $len) {
          // Escape all backslashes, but let the terminating
          // double quotation mark we add below be interpreted
          // as a metacharacter.
          $result .= str_repeat('\\', $numBackslashes * 2);
          break;
      } elseif ($value[$i] == '"') {
          // Escape all backslashes and the following double quotation mark.
          $result .= str_repeat('\\', $numBackslashes * 2 + 1);
          $result .= $value[$i];
      } else {
          // Backslashes aren't special here.
          $result .= str_repeat('\\', $numBackslashes);
          $result .= $value[$i];
      }
  }

  $result .= '"';

  return $result;
}

/**
 * Escapes all CMD metacharacters with a `^`.
 *
 * Adapted from https://blogs.msdn.microsoft.com/twistylittlepassagesallalike/2011/04/23/everyone-quotes-command-line-arguments-the-wrong-way/
 *
 * @param  string The argument to be escaped
 * @result string Escaped argument that can be used in CMD.exe
 */
function escapeWindowsCMD($value) {
  // Make sure this is CreateProcess-safe first
  $value = escapeWindowsArgv($value);

  // Now prefix all CMD meta characters with a `^` to escape them
  return preg_replace('/[()%!^"<>&|]/', '^$0', $value);
}

/* Some strings that are tested:

$edgeCases = array(
  '\0',  // null byte
  '\\',
  '%',
  '%%',
  ' ',  // space
  '',  // empty string
  '-',
  '/flag',
  '\\\^\%\\\'\ \\',
  '%PATH%',
  '%XYZ%',
  '%%HOMEDIR%',
  '\n',  // newline
  '\r',  // newline
  'a b',
  '"a b"',
  '"%%$HOMEDIR%^^"',
  '\'a b\'',
  '^%HO ^"M\'EDIR^%^%\'',
  '"\'a\0\r\nb%PATH%%`\'"\'`\'`\'',
);
*/
?>