[krapp]

If you look up the json_encode function on php.net it lists the flags. As I understand it there's a difference between the encoding allowed in javascript and the encoding allowed in JSON which means certain characters which would be valid in a javascript object don't necessarily work in JSON, so you end up having to escape everything possible. There's one flag (JSON_ESCAPE_UNICODE) which doesn't work on the version of PHP I develop on so I ended up applying code listed in the comments. This also adds some cruft similar to what google/facebook etc use if you want it. I haven't had any issues with it yet but, being what it is, there may be a more elegant way to accomplish it.

   function AsJSON($arr, $cruft=null){
		
	//convmap since 0x80 char codes so it takes all multibyte codes (above ASCII 127). 
	//So such characters are being "hidden" from normal json_encoding
        array_walk_recursive($arr, function (&$item, $key) {  	
        	if (is_string($item)){  
        		$item = mb_encode_numericentity($item, array (0x80, 0xffff, 0, 0xffff), 'UTF-8');
        	}
        });
        
        $JSON = mb_decode_numericentity(
        	json_encode($arr, JSON_HEX_TAG | JSON_HEX_APOS | JSON_HEX_QUOT | JSON_HEX_AMP), 
        	array (0x80, 0xffff, 0, 0xffff), 
        	'UTF-8'
        );

        if(json_last_error() === JSON_ERROR_NONE){ 
	  return $cruft.$JSON;
	 	}
	}

You might also consider looking at the ctype_* functions if you haven't.