json prettify in PHP

json_indent.php

/**
 * Indents a flat JSON string to make it more human-readable.
 *
 * http://www.daveperrett.com/articles/2008/03/11/format-json-with-php/
 */
function json_indent($json)
{
	$result      = '';
	$pos         = 0;
	$strLen      = strlen($json);
	$indentStr   = '  ';
	$newLine     = "\n";
	$prevChar    = '';
	$outOfQuotes = true;

	for ($i=0; $i<=$strLen; $i++)
	{
		// Grab the next character in the string.
		$char = substr($json, $i, 1);

		// Are we inside 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(($char == '}' || $char == ']') && $outOfQuotes) {
			$result .= $newLine;
			$pos --;
			for ($j=0; $j<$pos; $j++) {
				$result .= $indentStr;
			}
		}

		// Add the character to the result string.
		$result .= $char;

		// If the last character was the beginning of an element,
		// output a new line and indent the next line.
		if (($char == ',' || $char == '{' || $char == '[') && $outOfQuotes) {
			$result .= $newLine;
			if ($char == '{' || $char == '[') {
				$pos ++;
			}

			for ($j = 0; $j < $pos; $j++) {
				$result .= $indentStr;
			}
		}

		$prevChar = $char;
	}

	return $result;
}

or, echo json_encode(json_decode($json), JSON_PRETTY_PRINT);

Nice Pgee70 but if you want to have more control over the result like the number of white spaces for the indentation, this function becomes handy as JSON_PRETTY_PRINT does not allow this kind of customization.