PHP – JSON Indent Function

Starting from version 5.4.0, PHP function json_encode() has additional option, JSON_PRETTY_PRINT, determining whether json data should be formatted in a human readable format or not (the option itself is described as “Use whitespace in returned data to format it“).

But working for clients could have many challenges, so you’ll never be sure if they have perfect environment and proper software version or not.

So here is a PHP function for transforming and formatting json data in more human readable form:

/**
 * Indents a flat JSON string to make it more human-readable.
 *
 * @param string $json The original JSON string to process.
 * @return string Indented version of the original JSON string.
 */
function jsonIndent($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;
}