如何在PHP中动态构建<<< EOD字符串[关闭]

问题描述：

I want to build my string dynamically depending on the results from the DB. So far I have created something like this:

        $feed = Some essential xml that needs to go here;
        for ($a = 0; $a < count($images); $a++)
        {
            if ($a == 0)
            {
                $image_type = "Main";
            }
            else
            {
                $image_type = "PT". $a;
            }
            $feed += <<<EOD
  <Message>
    <MessageID>1</MessageID>
    <OperationType>Update</OperationType>
    <ProductImage>
        <SKU>{$data['sku']}</SKU>
        <ImageType>{$image_type}</ImageType>
        <ImageLocation>{$images[$a]}</ImageLocation>
    </ProductImage>
  </Message>
EOD;

        }

        $feed += <<<EOD
</AmazonEnvelope>        
EOD;
echo $feed;

This example of course returns nothing however I wanted to present my code in the way that I would like it to work. Do would I build the $feed string dynamically in this case?

我想根据数据库的结果动态构建我的字符串。到目前为止，我已经创建了这样的东西： p>

  $ feed =需要去的一些必要的xml; 
 for（$ a = 0; $ a＆lt; count（  $ images）; $ a ++）
 {
 if if（$ a == 0）
 {
 $ image_type =“Main”; 
} 
 else 
 {
 $ image_type =“PT”。  $ a; 
} 
 $ feed + =＆lt;＆lt;＆lt;＆lt; EOD 
＆lt;消息＆gt; 
＆lt;消息ID＆gt; 1＆lt; /消息ID＆gt; 
＆lt; OperationType＆gt;更新＆lt; / OperationType＆gt; 
＆lt;  ; ProductImage＆gt; 
＆lt; SKU＆gt; {$ data ['sku']}＆lt; / SKU＆gt; 
＆lt; ImageType＆gt; {$ image_type}＆lt; / ImageType＆gt; 
＆lt; ImageLocation＆gt; {$ images [$ a  ]}＆lt; / ImageLocation＆gt; 
＆lt; / ProductImage＆gt; 
＆lt; / Message＆gt; 
EOD; 
 
} 
 
 $ feed + =＆lt;＆lt;＆lt; EOD 
＆lt; / AmazonEnvelope＆gt;  
EOD; 
echo $ feed;  
  code>  pre> 
 
 这个例子当然没有返回任何内容，但我希望以我希望的方式呈现我的代码。 在这种情况下，我会动态构建$ feed字符串吗？   p> 
  div>

答

In PHP string concatenation is done with the . operator, not the +. Therefore concatenate and assign is also .=, not +=. Fix that in both relevant lines and it'll work fine.

The underlying reason for the different operator here is that, unlike most other popular languages, PHP is weak-typed. The + operator is as such reserved for mathematical operations, so PHP can handle these 2 different lines 'correctly':

echo '123'+'123';    // Shows 246
echo '123'.'123';    // Shows 123123

Example.

如何在PHP中动态构建<<< EOD字符串[关闭]

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