Simple Declarative Language (SDL) for PHP
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php-sdl 2.0

This is an implementation of the Simple Declarative Language (SDL) serialization language for PHP. It has not thing to do with Simple Directmedia Layer. Think of it like XML with less typing:

    greetings {
        greeting "Aloha" where="Hawaii"
        greeting "Hej" where="Sweden"

This is the v2.0 rewrite of php-sdl, and as such some things are not quite working yet. If you are looking for a working but not too extensible parser, install the v1.x branch with composer, composer require noccylabs/sdl:1.*. The current quirks are:

  • Not all LiteralTypes are implemented. This is easily done now however, as each type is in its own folder.
  • The parser is broken still.
  • Not all unit tests have been created.
  • Comments can be generated, but not necessarily always parsed.
  • Numeric types may lose precision.


You shouldn't really use this right now. Here is a brief summary of what is working, and what is not. Contributions and improvements are welcome.


Component Description Status
Sdl\SdlTag Creating tag trees WORKING
Sdl\SdlTag Encoding tags and children WORKING
Sdl\SdlTag Encoding tags with comments WORKING
Sdl\SdlTag Tree traversal WORKING
Sdl\SdlTag Tests implemented PARTIAL
Sdl\Parser\SdlParser Parsing tags and nested tags WORKING
Sdl\Parser\SdlParser Parsing tags with comments
Sdl\Parser\SdlParser Tests implemented PARTIAL
Sdl\LiteralType\TypeFactory LiteralType registering PARTIAL
Sdl\LiteralType\TypeFactory Tests implemented PARTIAL
Sdl\LiteralType\*Type All types implemented PARTIAL
Sdl\LiteralType\*Type Tests implemented PARTIAL
Sdl\Selector\SdlSelector Selecting with expressions PARTIAL
Sdl\Selector\SdlSelector Tests implemented


Function Status
Creating tag trees WORKING
Encoding tag trees into SDL WORKING
Parsing SDL into tag trees PARTIAL
Navigating the tag tree WORKING
Selecting tags with expressions PARTIAL
Create LiteralTypes from native PHP variable types WORKING
Create LiteralTypes from SDL tokens PARTIAL
Access LiteralTypes as native PHP values PARTIAL
Encode LiteralTypes into SDL tokens PARTIAL


The parser is currently a little slow at reading, but this can probably be optimized somewhat. Either way it offers a tidy alternative to the established serialization formats (XML, JSON and YAML). It is important to remember that the parsers for XML, JSON and YAML are running as native code, while the SDL parser is written in PHP.

That being said, it should be noted that php-sdl is best used with configuration files that are not being requested at an excessive frequency (such as blog posts, routing tables etc.) but rather for f.ex. job configurations, or immediate files (like dumping blogposts into sdl for easy editing and import).

Caching is implemented as it was in the 1.x version of the parser, i.e. the cache file with the parsed tags is placed in the same directory as the SDL-fil being parsed, with an identical filename except prefixed with a dot (.) and suffixed with ".cache". For example "foo.sdl" would be cached as ".foo.sdl.cache". This behaviour might change in the future.

Format Parser 10000x Calls/s
SDL SdlParser::parseString 8.83s 1132.50
XML DomDocument::loadXml 0.43s 23469.17
JSON json_decode 0.26s 38640.62
YAML yaml_parse_file 0.44s 22738.22

Some possible improvements and optimizations include:

  • Improvements to the pre-parser optimization routines.
  • Rewrite the parser using regular expressions (could be faster, could be slower)


Generating tag trees

Generating is simple. Get a new root tag with createRoot() and start adding your children. You can use the same fluid programming as you are used to from Symfony2, where all the setX() methods return the current tag, and a call to end() returns the parent node. createChild() is available to create a tag, add it as a child to the current node, and return the newly created child tag.

    use Sdl\SdlTag;
    $tag = SdlTag::createRoot()
                ->setValue("John Doe")
    echo $tag->encode();

Values and attributes can be assigned from PHP values, or directly via any of the LiteralType descendants.

    use Sdl\SdlTag;
    use Sdl\LiteralType\SdlBinary;
    $tag = SdlTag::createRoot()
            ->setValue(new SdlBinary($file))

Remember to match your calls to end() to make sure you return the root element when you are using the fluid method calls on a new root or non-variable:

    use Sdl\SdlTag;
    $tag = SdlTag::createRoot();
    // $tag will still point to the root even though end() wasn't called.
    $bad = SdlTag::createRoot()->createChild("foo")->createChild("bar");
    // $bad will be pointing to "bar" here, not the root.

You should however be able to get back to the root using getParent() if you ever needed to:

    function root($tag) {
        while(($parent = $tag->getParent())
            $tag = $parent;
        return $tag;

Parsing a file

To parse a file, use the Sdl\Parser\SdlParser class. It offers a few different methods to parse content and return Sdl\SdlTag objects.

    use Sdl\Parser\SdlParser;
    // Parse a file
    $tag = SdlParser::parseFile("basic.sdl");
    // Parse a string
    $tag = SdlParser::parseString($sdl_string);

Encoding tags to SDL

Tags are encoded into SDL using the encode() method. If you need to write it out to a file, use file_put_contents() or any other appropriate method to write out the output from encode().

    use Sdl\SdlTag;
    // Create a new root
    $tag = SdlTag::createRoot();
    // Add two children
    $tag->addChild("foo")->setValuesFromArray([0, 1, 2 ]);
    $tag->addChild("bar")->setValuesFromArray([2, 3, 4 ]);
    // Output the final SDL
    echo $tag->encode();

Navigating children

You can use getAllChildren(), getChildrenByTagName(..) to navigate the tree.

The SdlSelector will provide a more convenient approach to querying the tree with logical expressions.

    use Sdl\Parser\SdlParser;
    $tag = SdlTag::createRoot();
            ->setValue("John Doe")
    $people = $tag->getChildrenByTagName("people")[0]->getAllChildren();
    echo "Person name: ".$people[0]->getValue()."\n";

    // Enumerate children
    foreach($tag->getAllChildren() as $ctag) {
        printf("Tag: %s\n", $ctag->getTagName());


Queries make use of Symfony's ExpressionLanguage component to allow complex queries:

    use Sdl\Parser\SdlParser;
    use Sdl\Selector\SdlSelector;

    // Load the data
    $tag = SdlParser::parseFile(__DIR__."/sdl/products.sdl");
    // Create a new selector for the tag
    $tag_sel = new SdlSelector($tag);

    // Execute the query
    $expr = "/productcatalog/product[tag.attr('itemno')=='101-NAIL']";
    $item = $tag_sel->query($expr);


You can run the unit tests using phpunit:

  $ phpunit --bootstrap tests/bootstrap.php tests/src/

Just remember to create the autoloaders etc first using composer:

  $ composer dump-autoload

When contributing code, follow the conventions used elsewhere and send a pull request with your masterpiece. If you're too lazy to fix something yourself, or more likely busy saving the world elsewhere, create an issue so someone else can take care of it.