The Yaml Component

Fast

One of the goals of Symfony Yaml is to find the right balance between speed and features. It supports just the needed features to handle configuration files. Notable lacking features are: document directives, multi-line quoted messages, compact block collections and multi-document files.

Real Parser

It sports a real parser and is able to parse a large subset of the YAML specification, for all your configuration needs. It also means that the parser is pretty robust, easy to understand, and simple enough to extend.

Clear Error Messages

Whenever you have a syntax problem with your YAML files, the library outputs a helpful message with the filename and the line number where the problem occurred. It eases the debugging a lot.

Dump Support

It is also able to dump PHP arrays to YAML with object support, and inline level configuration for pretty outputs.

Types Support

It supports most of the YAML built-in types like dates, integers, octals, booleans, and much more...

Full Merge Key Support

Full support for references, aliases, and full merge key. Don't repeat yourself by referencing common configuration bits.

Reading YAML Files

The parse() method parses a YAML string and converts it to a PHP array:

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use Symfony\Component\Yaml\Yaml;

$value = Yaml::parse(file_get_contents('/path/to/file.yml'));

If an error occurs during parsing, the parser throws a ParseException exception indicating the error type and the line in the original YAML string where the error occurred:

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use Symfony\Component\Yaml\Exception\ParseException;

try {
    $value = Yaml::parse(file_get_contents('/path/to/file.yml'));
} catch (ParseException $exception) {
    printf("Unable to parse the YAML string: %s", $exception->getMessage());
}

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$object = Yaml::parse('{"foo": "bar"}', false, false, true);
echo get_class($object); // stdClass
echo $object->foo; // bar

Writing YAML Files

The dump() method dumps any PHP array to its YAML representation:

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use Symfony\Component\Yaml\Yaml;

$array = array(
    'foo' => 'bar',
    'bar' => array('foo' => 'bar', 'bar' => 'baz'),
);

$yaml = Yaml::dump($array);

file_put_contents('/path/to/file.yml', $yaml);

If an error occurs during the dump, the parser throws a DumpException exception.

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foo: bar
bar:
    foo: bar
    bar: baz

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echo Yaml::dump($array, 1);

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foo: bar
bar: { foo: bar, bar: baz }

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echo Yaml::dump($array, 2);

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foo: bar
bar:
    foo: bar
    bar: baz

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// uses 8 spaces for indentation
echo Yaml::dump($array, 2, 8);

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foo: bar
bar:
        foo: bar
        bar: baz

Invalid Types and Object Serialization

By default the YAML component will encode any "unsupported" type (i.e. resources and objects) as null.

Instead of encoding as null you can choose to throw an exception if an invalid type is encountered in either the dumper or parser as follows:

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// throws an exception if a resource or object is encountered
Yaml::dump($data, 2, 4, true);

// throws an exception if an encoded object is found in the YAML string
Yaml::parse($yaml, true);

However, you can activate object support using the next argument:

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$object = new \stdClass();
$object->foo = 'bar';

$dumped = Yaml::dump($object, 2, 4, false, true);
// !!php/object:O:8:"stdClass":1:{s:5:"foo";s:7:"bar";}

$parsed = Yaml::parse($dumped, false, true);
var_dump(is_object($parsed)); // true
echo $parsed->foo; // bar

The YAML component uses PHP's serialize() method to generate a string representation of the object.