Today I wanted a way to pretty-print a JSON string with colour highlighting. I went looking and found a bunch of ‘pretty print’ functions, but none with colour, so I implemented my own

Usage:

1. Include the relevant CSS for formatting your prettified JSON. There’s example CSS in the code below. You can do:

   echo("<style>".Convert::jsonPrettyHtmlCSS()."</style>");

2. Call Convert::json2PrettyHTML(), e.g:

   echo(Convert::json2PrettyHTML('["a",{"foo":"bar","baz":42}]'));

   ….And the code:

   
   <?php
   
   class Convert {
   	
   	/**
   	 * Helper for Convert::prettyJSON()
   	 * Returns a HTML <span> with a class matching the data type (integer,string,double,etc)
   	 * 	Add css to colour the values according to type.
   	 * 
   	 * autodetects numeric strings and treats them as numbers 
   	 * 
   	 * runs htmlentities() and wordwrap() on values (wraps at 100 chars)
   	 * 
   	 * @param mixed $val	value to beautify
   	 * @param int $indents	number of indents
   	 * @param bool $isKey	true if this is a key name
   	 * @return HTML
   	 * @see Convert::prettyJSON()
   	 * @see Convert::json2PrettyHTML() 
   	 * 
   	 */
   	private static function jsonColor($val,$indents=1,$isKey=false) {
   		//echo print_r($val,true) . ": " . gettype($val) . "\n";
   		$type = gettype($val);
   		
   		if (($type == "string") && is_numeric($val)) {
   			//try to convert it to a number
   			$val = floatval($val);
   			
   			if (intval($val) == $val)	//convert from float to int if it's a whole number: 
   				$val = intval($val);
   			
   			$type = gettype($val);
   		}
   		
   		//$type = gettype($val);
   		
   		$color = "";
   		switch($type) {
   			case 'string':
   				$val = '"' . $val . '"';
   				break;
   			case 'array':
   				$val = self::prettyJSON($val,$indents);
   				break;
   		}
   		$val = wordwrap(htmlentities($val),100,"<br />",true);
   		
   		if ($isKey) $type = $type . " key";
   		
   		return "<span class='$type'>" . //"' style='color:$color;'>" 
   			"$val</span>"; // . " (" . gettype($val) . ")";
   	}
   	
   	/**
   	 * Helper for Convert::json2PrettyHtml()
   	 * convert a value (i.e from json_decode) into a pretty colourised string
   	 * @param array|string|number $json		value to prettify
   	 * @param number $indents				indentation level (used for recursion)
   	 * @return string
   	 * @see Convert::json2PrettyHTML()
   	 */
   	private static function prettyJSON($json,$indents = 1) {
   		$ret = "";
   		$indent=str_repeat("<span class='indent'> </span>",$indents);
   		if (is_array($json) || is_object($json) ) {
   			foreach ($json as $k => $v) {
   				$k = htmlentities($k);
   				if (is_array($v) || is_object($v)) {
   					$v = self::prettyJson($v,$indents+1);
   					$ret .= ($ret ? ",<br />\n" : "") . $indent .
   						self::jsonColor($k,$indents,true) . ":\t<br />$v";
   				} else {
   					$ret .= ($ret ? ",<br />\n" : "") . $indent .
   						self::jsonColor($k,$indents,true) . ":\t" . self::jsonColor($v,$indents);
   				}
   			}
   			if (is_object($json)) {
   				$openbrace = "{";
   				$closebrace = "}";
   			} else {
   				$openbrace = "[";
   				$closebrace = "]";
   			}
   			$outdent=str_repeat("<span class='indent'> </span>",$indents-1);
   			$ret = "$outdent$openbrace<br />\n$ret<br />\n$outdent$closebrace";
   		} else
   			$ret = self::jsonColor($json,$indents);
   		
   		return $ret;
   		
   	}
   	
   		/**
   	 * Return or add some CSS for json2PrettyHTML to the requirements
   	 * @param string $return	if true, return the CSS. Otherwise insert it using Requirements::customCSS()
   	 * @return string | void
   	 * @see Convert::json2PrettyHTML()
   	 */
   	public static function jsonPrettyHtmlCSS($return = true) {
   		return 'span.json .integer, span.json .double {
   				color: #700;
   				font-family: mono;
   			}
   			
   			span.json .string {
   				color: #070;
   				font-family: mono;
   			}
   			
   			
   			span.json .key.string {
   				color: #007;
   			}
   			
   			span.json .key.integer, span.json .key.double {
   				color: #707;
   			}
   			
   			
   			span.json .indent {
   				padding-left: 40px;
   			}';
   	}
   	
   	/**
   	 * Converts a JSON string to pretty, readable HTML output which can be 
   	 * 	colourised/customised via CSS
   	 * 
   	 * Also does other nice things, like word wrapping at 100 chars, running 
   	 * 	values through htmlentities(), and treating numeric strings as numbers
   	 * 
   	 * Include CSS to style the output (set colours, indent width, etc)
   	 * Notes: 
   	 * 		- everything will be wrapped in a span.json (i.e <span> with 'json' 
   	 * 			as the class, css: span.json)
   	 * 		- keys will be spans with the'key' class  ( e.g span.key )
   	 * 		- values and keys will be spans and will have the datatype as the 
   	 * 			class ( span.integer, span.key.integer)
   	 * 		- there will be empty spans with the 'indent' class in the 
   	 * 			appropriate places. There may be more than one consecutively. 
   	 * 
   	 * Example CSS is returned by the jsonPrettyHtmlCSS() function
   			
   	 * @param string $json	the json to beautify
   	 * @return HTML
   	 * @see Convert::jsonPrettyHtmlCSS()
   	 */
   	public static function json2PrettyHTML($json) {
   		return "<span class='json'>" . self::prettyJSON(json_decode($json)) . "</span>";
   	}
   }
   
   
   
   

   I hope someone finds this useful!