Correct output:
'{"data":[{"id":"1","reason":"hello\\nworld"},{"id":"2","reason":"it\\nworks"}]}'
function json_entities( $data = null )
{
//stripslashes
return str_replace( '\n',"\\"."\\n",
htmlentities(
utf8_encode( json_encode( $data) ) ,
ENT_QUOTES | ENT_IGNORE, 'UTF-8'
)
);
}