php 编写一个简单的模板引擎

php web开发中广泛采取mvc的设计模式，controller传递给view层的数据，必须通过模板引擎才能解析出来。实现一个简单的仅仅包含if，foreach标签，解析$foo变量的模板引擎。 
编写template模板类和compiler编译类。代码如下：

<?php

namespace foo\base;
use foo\base\Object;
use foo\base\Compiler;
/**
* 
*/
class Template extends Object
{
    private $_config = [
        &#39;suffix&#39; => &#39;.php&#39;,//文件后缀名
        &#39;templateDir&#39; => &#39;../views/&#39;,//模板所在文件夹
        &#39;compileDir&#39; => &#39;../runtime/cache/views/&#39;,//编译后存放的目录
        &#39;suffixCompile&#39; => &#39;.php&#39;,//编译后文件后缀
        &#39;isReCacheHtml&#39; => false,//是否需要重新编译成静态html文件
        &#39;isSupportPhp&#39; => true,//是否支持php的语法
        &#39;cacheTime&#39; => 0,//缓存时间,单位秒
    ];
    private $_file;//带编译模板文件
    private $_valueMap = [];//键值对
    private $_compiler;//编译器

    public function __construct($compiler, $config = [])
    {
        $this->_compiler = $compiler;
        $this->_config = array_merge($this->_config, $config);
    }

    /**
     * [assign 存储控制器分配的键值]
     * @param  [type] $values [键值对集合]
     * @return [type]         [description]
     */
    public function assign($values)
    {
        if (is_array($values)) {
            $this->_valueMap = $values;
        } else {
            throw new \Exception(&#39;控制器分配给视图的值必须为数组!&#39;);
        }
        return $this;
    }

    /**
     * [show 展现视图]
     * @param  [type] $file [带编译缓存的文件]
     * @return [type]       [description]
     */
    public function show($file)
    {
        $this->_file = $file;
        if (!is_file($this->path())) {
            throw new \Exception(&#39;模板文件&#39;. $file . &#39;不存在!&#39;);
        }

        $compileFile = $this->_config[&#39;compileDir&#39;] . md5($file) . $this->_config[&#39;suffixCompile&#39;];
        $cacheFile = $this->_config[&#39;compileDir&#39;] . md5($file) . &#39;.html&#39;;

        //编译后文件不存在或者缓存时间已到期,重新编译,重新生成html静态缓存
        if (!is_file($compileFile) || $this->isRecompile($compileFile)) {
            $this->_compiler->compile($this->path(), $compileFile, $this->_valueMap);
            $this->_config[&#39;isReCacheHtml&#39;] = true;

            if ($this->isSupportPhp()) {
                extract($this->_valueMap, EXTR_OVERWRITE);//从数组中将变量导入到当前的符号表
            }

        }

        if ($this->isReCacheHtml()) {
            ob_start();
            ob_clean();
            include($compileFile);
            file_put_contents($cacheFile, ob_get_contents());
            ob_end_flush();
        } else {
            readfile($cacheFile);
        }
    }

    /**
     * [isRecompile 根据缓存时间判断是否需要重新编译]
     * @param  [type]  $compileFile [编译后的文件]
     * @return boolean              [description]
     */
    private function isRecompile($compileFile)
    {
        return time() - filemtime($compileFile) > $this->_config[&#39;cacheTime&#39;];
    }

    /**
     * [isReCacheHtml 是否需要重新缓存静态html文件]
     * @return boolean [description]
     */
    private function isReCacheHtml()
    {
        return $this->_config[&#39;isReCacheHtml&#39;];
    }

    /**
     * [isSupportPhp 是否支持php语法]
     * @return boolean [description]
     */
    private function isSupportPhp()
    {
        return $this->_config[&#39;isSupportPhp&#39;];
    }

    /**
     * [path 获得模板文件路径]
     * @return [type] [description]
     */
    private function path()
    {
        return $this->_config[&#39;templateDir&#39;] . $this->_file . $this->_config[&#39;suffix&#39;];
    }


}

<?php

namespace foo\base;
use foo\base\Object;

/**
* 
*/
class Compiler extends Object
{
    private $_content;
    private $_valueMap = [];
    private $_patten = [
        &#39;#\{\\$([a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*)\}#&#39;,
        &#39;#\{if (.*?)\}#&#39;,
        &#39;#\{(else if|elseif) (.*?)\}#&#39;,
        &#39;#\{else\}#&#39;,
        &#39;#\{foreach \\$([a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*)}#&#39;,
        &#39;#\{\/(foreach|if)}#&#39;,
        &#39;#\{\\^(k|v)\}#&#39;,
    ];
    private $_translation = [
        "<?php echo \$this->_valueMap[&#39;\\1&#39;]; ?>",
        &#39;<?php if (\\1) {?>&#39;,
        &#39;<?php } else if (\\2) {?>&#39;,
        &#39;<?php }else {?>&#39;,
        "<?php foreach (\$this->_valueMap[&#39;\\1&#39;] as \$k => \$v) {?>",
        &#39;<?php }?>&#39;,
        &#39;<?php echo \$\\1?>&#39;
    ];

    /**
     * [compile 编译模板文件]
     * @param  [type] $source   [模板文件]
     * @param  [type] $destFile [编译后文件]
     * @param  [type] $values   [键值对]
     * @return [type]           [description]
     */
    public function compile($source, $destFile, $values)
    {
        $this->_content = file_get_contents($source);
        $this->_valueMap = $values;

        if (strpos($this->_content, &#39;{$&#39;) !== false) {
            $this->_content = preg_replace($this->_patten, $this->_translation, $this->_content);
        }
        file_put_contents($destFile, $this->_content);
    }
}

我们的控制器就可以调用template中的assign方法进行赋值，show方法进行模板编译了。

<?php
namespace foo\base;
use foo\base\Object;

class Container extends Object
{
    private static $_instance;
    private $s = [];
    public static $instances = [];

    public static function getInstance()
    {
        if (!(self::$_instance instanceof self)) {
            self::$_instance = new self();
        }
        return self::$_instance;
    }

    private function __construct(){}

    private function __clone(){}

    public function __set($k, $c)
    {
        $this->s[$k] = $c;
    }

    public function __get($k)
    {
        return $this->build($this->s[$k]);
    }

    /**
     * 自动绑定（Autowiring）自动解析（Automatic Resolution）
     *
     * @param string $className
     * @return object
     * @throws Exception
     */
    public function build($className)
    {     
        // 如果是闭包函数（closures）
        if ($className instanceof \Closure) {
            // 执行闭包函数
            return $className($this);
        }

        if (isset(self::$instances[$className])) {
            return self::$instances[$className];
        }

        /** @var ReflectionClass $reflector */
        $reflector = new \ReflectionClass($className);

        // 检查类是否可实例化, 排除抽象类abstract和对象接口interface
        if (!$reflector->isInstantiable()) {
            throw new \Exception($reflector . &#39;: 不能实例化该类!&#39;);
        }

        /** @var ReflectionMethod $constructor 获取类的构造函数 */
        $constructor = $reflector->getConstructor();

        // 若无构造函数，直接实例化并返回
        if (is_null($constructor)) {
            return new $className;
        }

        // 取构造函数参数,通过 ReflectionParameter 数组返回参数列表
        $parameters = $constructor->getParameters();

        // 递归解析构造函数的参数
        $dependencies = $this->getDependencies($parameters);

        // 创建一个类的新实例，给出的参数将传递到类的构造函数。
        $obj = $reflector->newInstanceArgs($dependencies);
        self::$instances[$className] = $obj;

        return $obj;
    }

    /**
     * @param array $parameters
     * @return array
     * @throws Exception
     */
    public function getDependencies($parameters)
    {
        $dependencies = [];

        /** @var ReflectionParameter $parameter */
        foreach ($parameters as $parameter) {
            /** @var ReflectionClass $dependency */
            $dependency = $parameter->getClass();

            if (is_null($dependency)) {
                // 是变量,有默认值则设置默认值
                $dependencies[] = $this->resolveNonClass($parameter);
            } else {
                // 是一个类，递归解析
                $dependencies[] = $this->build($dependency->name);
            }
        }

        return $dependencies;
    }

    /**
     * @param ReflectionParameter $parameter
     * @return mixed
     * @throws Exception
     */
    public function resolveNonClass($parameter)
    {
        // 有默认值则返回默认值
        if ($parameter->isDefaultValueAvailable()) {
            return $parameter->getDefaultValue();
        }

        throw new \Exception(&#39;I have no idea what to do here.&#39;);
    }
}

要想以键值对的方式访问对象的属性必须实现ArrayAccess接口的四个方法， 
Object基类代码如下：

public function offsetExists($offset) 
    {
        return array_key_exists($offset, get_object_vars($this));
    }

    public function offsetUnset($key) 
    {
        if (array_key_exists($key, get_object_vars($this)) ) {
            unset($this->{$key});
        }
    }

    public function offsetSet($offset, $value) 
    {
        $this->{$offset} = $value;
    }

    public function offsetGet($var) 
    {
        return $this->$var;
    }

在某一控制器中就可以调用父类Controller的render方法啦

$this->render('test\index', ['name' => 'tom', 'age' => 20, 'friends' => ['jack', 'rose']], ['cacheTime' => 10]);

编写视图模板文件‘test\index’:

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>
<body>
   <p>展示模板文件视图</p> 
   <p>{$name}</p>
   <p>{$age}</p>
   <?php echo ++$age;?>
   {if $age > 18}
        <p>已成年</p>
    {else if $age < 10}
        <p>小毛孩</p>
   {/if}

   {foreach $friends} 
      <p>{^v} </p>
   {/foreach}
</body>
</html>

至此，一个简单的模板编译引擎就写好了。