构建自己的PHP框架--创建组件的机制
在之前的博客中，我们完成了基本的Model类，但是大家应该还记得，我们创建数据库的pdo实例时，是hard好的配置，并且直接hard在Model类中。
代码如下：
<code class="sourceCode php"> <span class="kw">public</span> <span class="kw">static</span> <span class="kw">function</span> getDb<span class="ot">()</span> { <span class="kw">if</span> <span class="ot">(</span><span class="fu">empty</span><span class="ot">(</span><span class="kw">static</span>::<span class="kw">$pdo</span><span class="ot">))</span> { <span class="kw">$host</span> = <span class="st">'localhost'</span><span class="ot">;</span> <span class="kw">$database</span> = <span class="st">'sf'</span><span class="ot">;</span> <span class="kw">$username</span> = <span class="st">'jun'</span><span class="ot">;</span> <span class="kw">$password</span> = <span class="st">'jun'</span><span class="ot">;</span> <span class="kw">$options</span> = <span class="ot">[</span> <span class="kw">PDO</span>::<span class="kw">ATTR_EMULATE_PREPARES</span> => <span class="kw">false</span><span class="ot">,</span> <span class="kw">PDO</span>::<span class="kw">ATTR_STRINGIFY_FETCHES</span> => <span class="kw">false</span> <span class="ot">];</span> <span class="kw">static</span>::<span class="kw">$pdo</span> = <span class="kw">new</span> <span class="kw">PDO</span><span class="ot">(</span><span class="st">"mysql:host=</span><span class="kw">$host</span><span class="st">;dbname=</span><span class="kw">$database</span><span class="st">"</span><span class="ot">,</span> <span class="kw">$username</span><span class="ot">,</span> <span class="kw">$password</span><span class="ot">,</span> <span class="kw">$options</span><span class="ot">);</span> <span class="kw">static</span>::<span class="kw">$pdo</span>-><span class="fu">exec</span><span class="ot">(</span><span class="st">"set names 'utf8'"</span><span class="ot">);</span> } <span class="kw">return</span> <span class="kw">static</span>::<span class="kw">$pdo</span><span class="ot">;</span> }</code>这明显是不合适的，修改的时候需要取修改框架的代码。现在我们就来将它抽出来。
首先我们需要将配置拿到相应的配置文件中，我们在simple-framework文件夹下创建一个config文件夹，然后添加一个db.php文件。在里面添加相关的配置。
代码如下：
<code class="sourceCode php"><span class="kw">return</span> <span class="ot">[</span> <span class="st">'class'</span> => <span class="st">'\PDO'</span><span class="ot">,</span> <span class="st">'dsn'</span> => <span class="st">'mysql:host=localhost;dbname=sf'</span><span class="ot">,</span> <span class="st">'username'</span> => <span class="st">'jun'</span><span class="ot">,</span> <span class="st">'password'</span> => <span class="st">'jun'</span><span class="ot">,</span> <span class="st">'options'</span> => <span class="ot">[</span> \<span class="kw">PDO</span>::<span class="kw">ATTR_EMULATE_PREPARES</span> => <span class="kw">false</span><span class="ot">,</span> \<span class="kw">PDO</span>::<span class="kw">ATTR_STRINGIFY_FETCHES</span> => <span class="kw">false</span><span class="ot">,</span> <span class="ot">],</span><span class="ot">];</span></code>
其实就是返回一个数组，数组中是我们创建pdo实例所需要的参数。在创建pdo实例之前，将db.php文件require进来即可。
代码如下：
<code class="sourceCode php"> <span class="kw">public</span> <span class="kw">static</span> <span class="kw">function</span> getDb<span class="ot">()</span> { <span class="kw">if</span> <span class="ot">(</span><span class="fu">empty</span><span class="ot">(</span><span class="kw">static</span>::<span class="kw">$pdo</span><span class="ot">))</span> { <span class="kw">$config</span> = <span class="kw">require</span><span class="ot">(</span><span class="st">'../config/db.php'</span><span class="ot">);</span> <span class="kw">static</span>::<span class="kw">$pdo</span> = <span class="kw">new</span> <span class="kw">$config</span><span class="ot">[</span><span class="st">'class'</span><span class="ot">](</span><span class="kw">$config</span><span class="ot">[</span><span class="st">'dsn'</span><span class="ot">],</span> <span class="kw">$config</span><span class="ot">[</span><span class="st">'username'</span><span class="ot">],</span> <span class="kw">$config</span><span class="ot">[</span><span class="st">'password'</span><span class="ot">],</span> <span class="kw">$config</span><span class="ot">[</span><span class="st">'options'</span><span class="ot">]);</span> <span class="kw">static</span>::<span class="kw">$pdo</span>-><span class="fu">exec</span><span class="ot">(</span><span class="st">"set names 'utf8'"</span><span class="ot">);</span> } <span class="kw">return</span> <span class="kw">static</span>::<span class="kw">$pdo</span><span class="ot">;</span> }</code>这样还是有点不爽，在require配置文件的时候，我需要一层层的去看相对位置，如果错了，就找不到了。而且将来不管是配置文件还是Model文件的位置变动了，相对位置就变了，我都需要修改这段代码。如果改成绝对地址是不是会好一些，至少配置文件位置不变，就不需要修改这段代码。
但是要改成绝对地址，我就需要定位simple-framework文件夹的地址，所以我们在public/index.php中define一个常量，标记simple-framework文件夹的地址。
public/index.php代码如下：
<code class="sourceCode php"><span class="kw"><?php</span><span class="fu">define</span><span class="ot">(</span><span class="st">'SF_PATH'</span><span class="ot">,</span> <span class="fu">dirname</span><span class="ot">(</span><span class="kw">__DIR__</span><span class="ot">));</span><span class="kw">require_once</span><span class="ot">(</span><span class="kw">SF_PATH</span> . <span class="st">'/vendor/autoload.php'</span><span class="ot">);</span><span class="kw">$application</span> = <span class="kw">new</span> sf\web\Application<span class="ot">();</span><span class="kw">$application</span>->run<span class="ot">();</span></code>
定义了常量SF_PATH，Model中的require可改为如下代码：
<code class="sourceCode php"><span class="kw">$config</span> = <span class="kw">require</span><span class="ot">(</span><span class="kw">SF_PATH</span> . <span class="st">'/config/db.php'</span><span class="ot">);</span></code>
OK，这样看起来好多了。
但是我又想到，假设将来我又需要一个cache的实例，我是不是又要把getDb的方法写一遍呢？如果要避免这种情况，我是不是应该把它抽想出来呢？那要如何抽象呢？
这个时候我们可能需要有一个方法，我们只需要告诉它我们需要创建一个什么实例，然后它就自己去取相应的参数，并创建出相应的实例来。这样是不是很爽。
我们需要在src文件夹下创建一个Sf.php，在其中创建一个createObject方法，用来创建实例。
但这个时候我们又遇到一个问题，pdo实例创建的时候，要按一定的顺序传一定个数的参数，但我们之后需要创建的其它的实例，可能传递的参数的个数和key都不同，那我们该怎么办？
所以我们需要一种机制能够将参数存起来，真正创建实例时，再取出来使用。我们可以在src/db文件夹下创建一个Connection类，Sf中的createObject方法创建了这个类的实例，这个类提供一个创建pdo实例的方法即可。
Sf.php中的代码如下：
<code class="sourceCode php"><span class="kw"><?php</span><span class="co">/**</span><span class="co"> * Sf is a helper class serving common framework functionalities.</span><span class="co"> * </span><span class="kw">@author</span><span class="co"> Harry Sun </span><span class="kw"><sunguangjun</span><span class="ot">@126.com</span><span class="kw">></span><span class="co"> */</span><span class="kw">class</span> Sf{ <span class="co">/**</span><span class="co"> * Creates a new object using the given configuration.</span><span class="co"> * You may view this method as an enhanced version of the `new` operator.</span><span class="co"> * </span><span class="kw">@param</span><span class="co"> </span><span class="kw">string</span><span class="co"> $name the object name</span><span class="co"> */</span> <span class="kw">public</span> <span class="kw">static</span> <span class="kw">function</span> createObject<span class="ot">(</span><span class="kw">$name</span><span class="ot">)</span> { <span class="kw">$config</span> = <span class="kw">require</span><span class="ot">(</span><span class="kw">SF_PATH</span> . <span class="st">"/config/</span><span class="kw">$name</span><span class="st">.php"</span><span class="ot">);</span> <span class="co">// create instance</span> <span class="kw">$instance</span> = <span class="kw">new</span> <span class="kw">$config</span><span class="ot">[</span><span class="st">'class'</span><span class="ot">]();</span> <span class="fu">unset</span><span class="ot">(</span><span class="kw">$config</span><span class="ot">[</span><span class="st">'class'</span><span class="ot">]);</span> <span class="co">// add attributes</span> <span class="kw">foreach</span> <span class="ot">(</span><span class="kw">$config</span> <span class="kw">as</span> <span class="kw">$key</span> => <span class="kw">$value</span><span class="ot">)</span> { <span class="kw">$instance</span>-><span class="kw">$key</span> = <span class="kw">$value</span><span class="ot">;</span> } <span class="kw">return</span> <span class="kw">$instance</span><span class="ot">;</span> }}</code>Sf类没有namespace，所以不符合psr4的规则，需要手动引入，在public/index.php中加入如下一句话：
<code class="sourceCode php"><span class="kw">require_once</span><span class="ot">(</span><span class="kw">SF_PATH</span> . <span class="st">'/src/Sf.php'</span><span class="ot">);</span></code>
Connection.php中的代码如下：
<code class="sourceCode php"><span class="kw"><?php</span><span class="kw">namespace</span> sf\db<span class="ot">;</span><span class="kw">use</span> <span class="kw">PDO</span><span class="ot">;</span><span class="co">/**</span><span class="co"> * Connection represents a connection to a database via [PDO](php.net/manual/en/book.pdo.php).</span><span class="co"> * </span><span class="kw">@author</span><span class="co"> Harry Sun </span><span class="kw"><sunguangjun</span><span class="ot">@126.com</span><span class="kw">></span><span class="co"> */</span><span class="kw">class</span> Connection{ <span class="co">/**</span><span class="co"> * </span><span class="kw">@var</span><span class="co"> </span><span class="st">string</span><span class="co"> </span><span class="st">the</span><span class="co"> </span><span class="st">Data</span><span class="co"> </span><span class="st">Source</span><span class="co"> </span><span class="st">Name,</span><span class="co"> </span><span class="st">or</span><span class="co"> </span><span class="st">DSN,</span><span class="co"> </span><span class="st">contains</span><span class="co"> </span><span class="st">the</span><span class="co"> </span><span class="st">information</span><span class="co"> </span><span class="st">required</span><span class="co"> </span><span class="st">to</span><span class="co"> </span><span class="st">connect</span><span class="co"> </span><span class="st">to</span><span class="co"> </span><span class="st">the</span><span class="co"> </span><span class="st">database.</span><span class="co"> * Please refer to the [PHP manual](http://www.php.net/manual/en/function.PDO-construct.php) on</span><span class="co"> * the format of the DSN string.</span><span class="co"> * </span><span class="kw">@see</span><span class="co"> charset</span><span class="co"> */</span> <span class="kw">public</span> <span class="kw">$dsn</span><span class="ot">;</span> <span class="co">/**</span><span class="co"> * </span><span class="kw">@var</span><span class="co"> </span><span class="st">string</span><span class="co"> </span><span class="st">the</span><span class="co"> </span><span class="st">username</span><span class="co"> </span><span class="st">for</span><span class="co"> </span><span class="st">establishing</span><span class="co"> </span><span class="st">DB</span><span class="co"> </span><span class="st">connection.</span><span class="co"> </span><span class="st">Defaults</span><span class="co"> </span><span class="st">to</span><span class="co"> </span><span class="st">`null`</span><span class="co"> </span><span class="st">meaning</span><span class="co"> </span><span class="st">no</span><span class="co"> </span><span class="st">username</span><span class="co"> </span><span class="st">to</span><span class="co"> </span><span class="st">use.</span><span class="co"> */</span> <span class="kw">public</span> <span class="kw">$username</span><span class="ot">;</span> <span class="co">/**</span><span class="co"> * </span><span class="kw">@var</span><span class="co"> </span><span class="st">string</span><span class="co"> </span><span class="st">the</span><span class="co"> </span><span class="st">password</span><span class="co"> </span><span class="st">for</span><span class="co"> </span><span class="st">establishing</span><span class="co"> </span><span class="st">DB</span><span class="co"> </span><span class="st">connection.</span><span class="co"> </span><span class="st">Defaults</span><span class="co"> </span><span class="st">to</span><span class="co"> </span><span class="st">`null`</span><span class="co"> </span><span class="st">meaning</span><span class="co"> </span><span class="st">no</span><span class="co"> </span><span class="st">password</span><span class="co"> </span><span class="st">to</span><span class="co"> </span><span class="st">use.</span><span class="co"> */</span> <span class="kw">public</span> <span class="kw">$password</span><span class="ot">;</span> <span class="co">/**</span><span class="co"> * </span><span class="kw">@var</span><span class="co"> </span><span class="st">array</span><span class="co"> </span><span class="st">PDO</span><span class="co"> </span><span class="st">attributes</span><span class="co"> </span><span class="st">(name</span><span class="co"> </span><span class="st">=></span><span class="co"> </span><span class="st">value)</span><span class="co"> * to establish a DB connection. Please refer to the</span><span class="co"> * [PHP manual](http://www.php.net/manual/en/function.PDO-setAttribute.php) for</span><span class="co"> * details about available attributes.</span><span class="co"> */</span> <span class="kw">public</span> <span class="kw">$attributes</span><span class="ot">;</span> <span class="kw">public</span> <span class="kw">function</span> getDb<span class="ot">()</span> { <span class="kw">return</span> <span class="kw">new</span> <span class="kw">PDO</span><span class="ot">(</span><span class="kw">$this</span>->dsn<span class="ot">,</span> <span class="kw">$this</span>->username<span class="ot">,</span> <span class="kw">$this</span>->password<span class="ot">,</span> <span class="kw">$this</span>->attributes<span class="ot">);</span> }}</code>虽然不显示声明dsn/username/password和attributes属性也是可行的，但我觉得还是声明出来比较好，这样大家看到这个类的时候，会知道有哪些属性。
Model类中的getDb方法改成如下代码：
<code class="sourceCode php"> <span class="kw">public</span> <span class="kw">static</span> <span class="kw">function</span> getDb<span class="ot">()</span> { <span class="kw">if</span> <span class="ot">(</span><span class="fu">empty</span><span class="ot">(</span><span class="kw">static</span>::<span class="kw">$pdo</span><span class="ot">))</span> { <span class="kw">static</span>::<span class="kw">$pdo</span> = Sf::createObject<span class="ot">(</span><span class="st">'db'</span><span class="ot">)</span>->getDb<span class="ot">();</span> <span class="kw">static</span>::<span class="kw">$pdo</span>-><span class="fu">exec</span><span class="ot">(</span><span class="st">"set names 'utf8'"</span><span class="ot">);</span> } <span class="kw">return</span> <span class="kw">static</span>::<span class="kw">$pdo</span><span class="ot">;</span> }</code>不要忘记需要use一下Sf。
config中的db.php也要跟着修改，代码如下：
<code class="sourceCode php"><span class="kw"><?php</span><span class="kw">return</span> <span class="ot">[</span> <span class="st">'class'</span> => <span class="st">'\sf\db\Connection'</span><span class="ot">,</span> <span class="st">'dsn'</span> => <span class="st">'mysql:host=localhost;dbname=sf'</span><span class="ot">,</span> <span class="st">'username'</span> => <span class="st">'jun'</span><span class="ot">,</span> <span class="st">'password'</span> => <span class="st">'jun'</span><span class="ot">,</span> <span class="st">'attributes'</span> => <span class="ot">[</span> \<span class="kw">PDO</span>::<span class="kw">ATTR_EMULATE_PREPARES</span> => <span class="kw">false</span><span class="ot">,</span> \<span class="kw">PDO</span>::<span class="kw">ATTR_STRINGIFY_FETCHES</span> => <span class="kw">false</span><span class="ot">,</span> <span class="ot">],</span><span class="ot">];</span></code>
我默默的将options换成了attributes，毕竟在PDO的文档里，写的是attribute。
好了，今天就先到这里。项目内容和博客内容也都会放到Github上，欢迎大家提建议。
code：https://github.com/CraryPrimitiveMan/simple-framework/tree/0.8
blog project：https://github.com/CraryPrimitiveMan/create-your-own-php-framework
