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I've read about hydration in doctrine's documentation but I still can't understand what it is.

Could someone please explain?

Denis Kulagin
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never_had_a_name
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    Not constructive? This is one of the most fundamental concepts for understanding how the Doctrine internals work. – csvan Jul 07 '14 at 09:06
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    I think this question should be protected rather than closed. – Simon Jan 30 '15 at 16:17
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    @Simon Agree. Question and the accepted answer are both popular, why not move it to _protected_ state then? – Denis Kulagin Jul 05 '16 at 08:43
  • Doctrine2 documentation reference explaining HYDRATION: http://www.doctrine-project.org/docs/orm/2.0/en/reference/dql-doctrine-query-language.html#query-result-formats – Dawid Ohia Sep 05 '11 at 13:08

2 Answers2

93

Hydration is a method used to return query results. For example:

  1. HYDRATE_ARRAY - This will return you an array of records that are represented by another array:

    $q = Doctrine_Query::create()
   ->from('Post p')
   ->setHydrationMode(Doctrine::HYDRATE_ARRAY);

$resultSet = $q->execute(); // $resultSet is an array

foreach ($resultSet as $post) {
    // $post is an array
    echo $post['title'];
}

  2. HYDRATE_RECORD - This will return you an collection (Doctrine_Collection) of objects:

    $q = Doctrine_Query::create()
   ->from('Post p')
   ->setHydrationMode(Doctrine::HYDRATE_RECORD); // Unnecessary, HYDATE_RECORD is default method

$resultSet = $q->execute(); // $resultSet is an Doctrine_Collection object

foreach ($resultSet as $post) {
    // $post is an Post object
    echo $post->getTitle();
    echo $post['title']; // Each Doctrine's Model object implements ArrayAccess interface so this is possible
    echo $post->myCustomMethod();
}

  3. HYDRATE_SINGULAR_SCALAR - Will return the value of first column of query's result:

     $q = Doctrine_Query::create()
   ->select('p.created_at')
   ->from('Post p')
   ->where('p.id = ?', 321)
   ->setHydrationMode(Doctrine::HYDRATE_SINGULAR_SCALAR); 

$createdAt = $q->execute(); // $createdAt has value of first column from first record from result set (eg.: 2008-04-06 21:22:35)

There is a few more methods , you can read about each in documentation.

Crozin
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  • ok..so normally when i use sql it returns a mysql object and i have to use mysqli_fetch_assoc, then sort them by myself and so on...but now its all sorted for me. that is what hydration is about, giving me sorted objects/arrays? – never_had_a_name Apr 18 '10 at 10:49
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    No, it's not about sorting result (`orderBy()` handle this). It is about *What will your query result*, whether it will be a single scalar value (`HYDRATE_SINGULAR_SCALAR`), an array or arrays where nested arrays represent each database record (`HYDRATE_ARRAY`) or a collection of objects (`HYDRATE_RECORD`). Do [var_dump](http://pl.php.net/manual/en/function.var-dump.php) on query result for each hydration mode - that's the best way to see "how it works?" – Crozin Apr 18 '10 at 11:24
  • aha..i think i get it now. so it's about what form i want the result to be in: scalar value, arrays or objects? that sounds like a very nice feature. than i dont have to convert them myself from mysqli_object:) – never_had_a_name Apr 19 '10 at 10:10
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    just a little tip. In 1.2 `HYDRATE_SINGULAR_SCALAR` returns an undefined constant error. `HYDRATE_SINGLE_SCALAR` is right. – Darmen Amanbay Nov 01 '11 at 10:33
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    As a note `Doctrine::HYDRATE_RECORD` is now known as `Doctrine::HYDRATE_OBJECT` – Steve Tauber Mar 03 '14 at 13:55
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    A link to the aforementioned documentation would make this answer more helpful. – Sean the Bean Sep 18 '15 at 20:32
2
$q->fetchOne(array(), Doctrine_Core::HYDRATE_ARRAY);

It will return just a simple array instead of a doctrine collection object.

hatef
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Jubayer Arefin
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