Pretty-print a JSON string in PHP.

pretty-json.php

<?php

	/**
	 * Formats a JSON string for pretty printing
	 *
	 * @param string $json The JSON to make pretty
	 * @param bool $html Insert nonbreaking spaces and <br />s for tabs and linebreaks
	 * @return string The prettified output
	 * @author Jay Roberts
	 */
         function _format_json($json, $html = false) {
		$tabcount = 0; 
		$result = ''; 
		$inquote = false; 
		$ignorenext = false; 

		if ($html) { 
		    $tab = "&nbsp;&nbsp;&nbsp;"; 
		    $newline = "<br/>"; 
		} else { 
		    $tab = "\t"; 
		    $newline = "\n"; 
		} 

		for($i = 0; $i < strlen($json); $i++) { 
		    $char = $json[$i]; 

		    if ($ignorenext) { 
		        $result .= $char; 
		        $ignorenext = false; 
		    } else { 
		        switch($char) { 
		            case '{': 
		                $tabcount++; 
		                $result .= $char . $newline . str_repeat($tab, $tabcount); 
		                break; 
		            case '}': 
		                $tabcount--; 
		                $result = trim($result) . $newline . str_repeat($tab, $tabcount) . $char; 
		                break; 
		            case ',': 
		                $result .= $char . $newline . str_repeat($tab, $tabcount); 
		                break; 
		            case '"': 
		                $inquote = !$inquote; 
		                $result .= $char; 
		                break; 
		            case '\\': 
		                if ($inquote) $ignorenext = true; 
		                $result .= $char; 
		                break; 
		            default: 
		                $result .= $char; 
		        } 
		    } 
		} 

		return $result; 
	}

Why don't we just use the json_decode() with JSON_PRETTY_PRINT option? The function usage is as follows:

json_encode(['key' => 'value'], JSON_PRETTY_PRINT)

Just provide the following this _format_json function and json_encode difference.

>>> json_encode(['key' => 'value'], JSON_PRETTY_PRINT)
=> """
   {\n
       "key": "value"\n
   }
   """
>>> _format_json(json_encode(['key' => 'value']))
=> """
   {\n
   \t"key":"value"\n
   }
   """
>>> 

It seems that these are different formatted JSON string, but their purposes are same.