graphql-php/concepts/index.html
2018-11-27 20:06:49 +07:00

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<a class="" href="../getting-started/">Getting Started</a>
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<a class="" href="../complementary-tools/">Complementary Tools</a>
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<span class="caption-text">Type Definitions</span>
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<a class="" href="../type-system/">Introduction</a>
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<a class="" href="../type-system/object-types/">Object Types</a>
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<a class="" href="../type-system/scalar-types/">Scalar Types</a>
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<a class="" href="../type-system/interfaces/">Interfaces</a>
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<a class="" href="../type-system/unions/">Unions</a>
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<a class="" href="../type-system/input-types/">Mutations and Input Types</a>
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<a class="" href="../type-system/directives/">Directives</a>
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<a class="" href="../type-system/schema/">Schema</a>
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<a class="" href="../type-system/type-language/">Using Type Language</a>
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<h1 id="overview">Overview</h1>
<p>GraphQL is data-centric. On the very top level it is built around three major concepts:
<strong>Schema</strong>, <strong>Query</strong> and <strong>Mutation</strong>.</p>
<p>You are expected to express your application as <strong>Schema</strong> (aka Type System) and expose it
with single HTTP endpoint (e.g. using our <a href="../executing-queries/#using-server">standard server</a>).
Application clients (e.g. web or mobile clients) send <strong>Queries</strong>
to this endpoint to request structured data and <strong>Mutations</strong> to perform changes (usually with HTTP POST method).</p>
<h2 id="queries">Queries</h2>
<p>Queries are expressed in simple language that resembles JSON:</p>
<pre><code class="graphql">{
hero {
name
friends {
name
}
}
}
</code></pre>
<p>It was designed to mirror the structure of expected response:</p>
<pre><code class="json">{
&quot;hero&quot;: {
&quot;name&quot;: &quot;R2-D2&quot;,
&quot;friends&quot;: [
{&quot;name&quot;: &quot;Luke Skywalker&quot;},
{&quot;name&quot;: &quot;Han Solo&quot;},
{&quot;name&quot;: &quot;Leia Organa&quot;}
]
}
}
</code></pre>
<p><strong>graphql-php</strong> runtime parses Queries, makes sure that they are valid for given Type System
and executes using <a href="../data-fetching/">data fetching tools</a> provided by you
as a part of integration. Queries are supposed to be idempotent.</p>
<h2 id="mutations">Mutations</h2>
<p>Mutations use advanced features of the very same query language (like arguments and variables)<br />
and have only semantic difference from Queries:</p>
<pre><code class="graphql">mutation CreateReviewForEpisode($ep: Episode!, $review: ReviewInput!) {
createReview(episode: $ep, review: $review) {
stars
commentary
}
}
</code></pre>
<p>Variables <code>$ep</code> and <code>$review</code> are sent alongside with mutation. Full HTTP request might look like this:</p>
<pre><code class="json">// POST /graphql-endpoint
// Content-Type: application/javascript
//
{
&quot;query&quot;: &quot;mutation CreateReviewForEpisode...&quot;,
&quot;variables&quot;: {
&quot;ep&quot;: &quot;JEDI&quot;,
&quot;review&quot;: {
&quot;stars&quot;: 5,
&quot;commentary&quot;: &quot;This is a great movie!&quot;
}
}
}
</code></pre>
<p>As you see variables may include complex objects and they will be correctly validated by
<strong>graphql-php</strong> runtime.</p>
<p>Another nice feature of GraphQL mutations is that they also hold the query for data to be
returned after mutation. In our example mutation will return:</p>
<pre><code>{
&quot;createReview&quot;: {
&quot;stars&quot;: 5,
&quot;commentary&quot;: &quot;This is a great movie!&quot;
}
}
</code></pre>
<h1 id="type-system">Type System</h1>
<p>Conceptually GraphQL type is a collection of fields. Each field in turn
has it's own type which allows to build complex hierarchies.</p>
<p>Quick example on pseudo-language:</p>
<pre><code>type BlogPost {
title: String!
author: User
body: String
}
type User {
id: Id!
firstName: String
lastName: String
}
</code></pre>
<p>Type system is a heart of GraphQL integration. That's where <strong>graphql-php</strong> comes into play.</p>
<p>It provides following tools and primitives to describe your App as hierarchy of types:</p>
<ul>
<li>Primitives for defining <strong>objects</strong> and <strong>interfaces</strong></li>
<li>Primitives for defining <strong>enumerations</strong> and <strong>unions</strong></li>
<li>Primitives for defining custom <strong>scalar types</strong></li>
<li>Built-in scalar types: <code>ID</code>, <code>String</code>, <code>Int</code>, <code>Float</code>, <code>Boolean</code></li>
<li>Built-in type modifiers: <code>ListOf</code> and <code>NonNull</code></li>
</ul>
<p>Same example expressed in <strong>graphql-php</strong>:</p>
<pre><code class="php">&lt;?php
use GraphQL\Type\Definition\Type;
use GraphQL\Type\Definition\ObjectType;
$userType = new ObjectType([
'name' =&gt; 'User',
'fields' =&gt; [
'id' =&gt; Type::nonNull(Type::id()),
'firstName' =&gt; Type::string(),
'lastName' =&gt; Type::string()
]
]);
$blogPostType = new ObjectType([
'name' =&gt; 'BlogPost',
'fields' =&gt; [
'title' =&gt; Type::nonNull(Type::string()),
'author' =&gt; $userType
]
]);
</code></pre>
<h1 id="further-reading">Further Reading</h1>
<p>To get deeper understanding of GraphQL concepts - <a href="http://graphql.org/learn/">read the docs on official GraphQL website</a></p>
<p>To get started with <strong>graphql-php</strong> - continue to next section <a href="../getting-started/">"Getting Started"</a></p>
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