<?php
// original code: http://www.daveperrett.com/articles/2008/03/11/format-json-with-php/
// adapted to allow native functionality in php version >= 5.4.0
/**
* Format a flat JSON string to make it more human-readable
*
* @param string $json The original JSON string to process
*        When the input is not a string it is assumed the input is RAW
*        and should be converted to JSON first of all.
* @return string Indented version of the original JSON string
*/
function json_format($json) {
  if (!is_string($json)) {
    if (phpversion() && phpversion() >= 5.4) {
      return json_encode($json, JSON_PRETTY_PRINT);
    }
    $json = json_encode($json);
  }
  $result      = '';
  $pos         = 0;               // indentation level
  $strLen      = strlen($json);
  $indentStr   = "\t";
  $newLine     = "\n";
  $prevChar    = '';
  $outOfQuotes = true;
  for ($i = 0; $i < $strLen; $i++) {
    // Speedup: copy blocks of input which don't matter re string detection and formatting.
    $copyLen = strcspn($json, $outOfQuotes ? " \t\r\n\",:[{}]" : "\\\"", $i);
    if ($copyLen >= 1) {
      $copyStr = substr($json, $i, $copyLen);
      // Also reset the tracker for escapes: we won't be hitting any right now
      // and the next round is the first time an 'escape' character can be seen again at the input.
      $prevChar = '';
      $result .= $copyStr;
      $i += $copyLen - 1;      // correct for the for(;;) loop
      continue;
    }
    
    // Grab the next character in the string
    $char = substr($json, $i, 1);
    
    // Are we inside a quoted string encountering an escape sequence?
    if (!$outOfQuotes && $prevChar === '\\') {
      // Add the escaped character to the result string and ignore it for the string enter/exit detection:
      $result .= $char;
      $prevChar = '';
      continue;
    }
    // Are we entering/exiting a quoted string?
    if ($char === '"' && $prevChar !== '\\') {
      $outOfQuotes = !$outOfQuotes;
    }
    // If this character is the end of an element,
    // output a new line and indent the next line
    else if ($outOfQuotes && ($char === '}' || $char === ']')) {
      $result .= $newLine;
      $pos--;
      for ($j = 0; $j < $pos; $j++) {
        $result .= $indentStr;
      }
    }
    // eat all non-essential whitespace in the input as we do our own here and it would only mess up our process
    else if ($outOfQuotes && false !== strpos(" \t\r\n", $char)) {
      continue;
    }
    // Add the character to the result string
    $result .= $char;
    // always add a space after a field colon:
    if ($outOfQuotes && $char === ':') {
      $result .= ' ';
    }
    // If the last character was the beginning of an element,
    // output a new line and indent the next line
    else if ($outOfQuotes && ($char === ',' || $char === '{' || $char === '[')) {
      $result .= $newLine;
      if ($char === '{' || $char === '[') {
        $pos++;
      }
      for ($j = 0; $j < $pos; $j++) {
        $result .= $indentStr;
      }
    }
    $prevChar = $char;
  }
  return $result;
}