PHP API Client Code

To use PlantUML image generation, a text diagram description have to be :

  1. Encoded in UTF-8

  2. Compressed using Deflate algorithm

  3. Reencoded in ASCII using a transformation close to base64

This is exactly what the following encodep() function is doing.

<?php

function encodep($text) {
     $data = utf8_encode($text);
     $compressed = gzdeflate($data, 9);
     return encode64($compressed);
}

function encode6bit($b) {
     if ($b < 10) {
          return chr(48 + $b);
     }
     $b -= 10;
     if ($b < 26) {
          return chr(65 + $b);
     }
     $b -= 26;
     if ($b < 26) {
          return chr(97 + $b);
     }
     $b -= 26;
     if ($b == 0) {
          return '-';
     }
     if ($b == 1) {
          return '_';
     }
     return '?';
}

function append3bytes($b1, $b2, $b3) {
     $c1 = $b1 >> 2;
     $c2 = (($b1 & 0x3) << 4) | ($b2 >> 4);
     $c3 = (($b2 & 0xF) << 2) | ($b3 >> 6);
     $c4 = $b3 & 0x3F;
     $r = "";
     $r .= encode6bit($c1 & 0x3F);
     $r .= encode6bit($c2 & 0x3F);
     $r .= encode6bit($c3 & 0x3F);
     $r .= encode6bit($c4 & 0x3F);
     return $r;
}

function encode64($c) {
     $str = "";
     $len = strlen($c);
     for ($i = 0; $i < $len; $i+=3) {
            if ($i+2==$len) {
                  $str .= append3bytes(ord(substr($c, $i, 1)), ord(substr($c, $i+1, 1)), 0);
            } else if ($i+1==$len) {
                  $str .= append3bytes(ord(substr($c, $i, 1)), 0, 0);
            } else {
                  $str .= append3bytes(ord(substr($c, $i, 1)), ord(substr($c, $i+1, 1)),
                      ord(substr($c, $i+2, 1)));
            }
     }
     return $str;
}
?>

Installing with Composer

You can install these functions with Composer:

$ composer require jawira/plantuml-encoding

Do not forget to import the encodep() function to use it:

<?php
require __DIR__ . '/vendor/autoload.php';
use function Jawira\PlantUml\encodep;

$encode = encodep('Alice -> Bob: hello');
echo "http://www.plantuml.com/plantuml/uml/{$encode}";