基于php双引号中访问数组元素报错的解决方法

最近在做微信公众号开发，在一个发送图文接口中，需要把数组元素拼接在XML字符串中

foreach ($itemArr as $key => $value){   $items .= "<item>   <Title><![CDATA[$value['title']]]></Title>    <Description><![CDATA[[$value['description']]]></Description>   <PicUrl><![CDATA[$value['picUrl']]]></PicUrl>   <Url><![CDATA[$value['url']]]></Url>   </item>"; } 

结果竟报如下错误信息：

Parse error: syntax error, unexpected '' (T_ENCAPSED_AND_WHITESPACE), expecting identifier (T_STRING) or variable (T_VARIABLE) or number (T_NUM_STRING) in D:/hhp/wamp/www/weixin/wx_sample.php on line 146

从错误信息看是单引号的问题，果断去掉之后就没报错了。然而我就纳闷了，引用下标为字符串的数组元素难道不该加引号吗？到php官方手册去查了关于数组的描述，有一段是这样的：

$arr = array('fruit' => 'apple', 'veggie' => 'carrot'); // This will not work, and will result in a parse error, such as: // Parse error: parse error, expecting T_STRING' or T_VARIABLE' or T_NUM_STRING' // This of course applies to using superglobals in strings as well print "Hello $arr['fruit']"; print "Hello $_GET['foo']"; 

这里给出了两种错误的写法，当一个普通数组变量或超全局数组变量包含在双引号中时，引用索引为字符串的数组元素，索引字符串不应该再添加单引号。那正确的写法是怎样的呢？于是我继续查找官方手册，找到如下说法：

$arr = array('fruit' => 'apple', 'veggie' => 'carrot');// This defines a constant to demonstrate what's going on. The value 'veggie'// is assigned to a constant named fruit.define('fruit', 'veggie');// The following is okay, as it's inside a string. Constants are not looked for// within strings, so no E_NOTICE occurs hereprint "Hello $arr[fruit]";   // Hello apple// With one exception: braces surrounding arrays within strings allows constants// to be interpretedprint "Hello {$arr[fruit]}";  // Hello carrotprint "Hello {$arr['fruit']}"; // Hello apple$arr = array('fruit' => 'apple', 'veggie' => 'carrot');// This defines a constant to demonstrate what's going on. The value 'veggie'// is assigned to a constant named fruit.define('fruit', 'veggie');// The following is okay, as it's inside a string. Constants are not looked for// within strings, so no E_NOTICE occurs hereprint "Hello $arr[fruit]";   // Hello apple// With one exception: braces surrounding arrays within strings allows constants// to be interpretedprint "Hello {$arr[fruit]}";  // Hello carrotprint "Hello {$arr['fruit']}"; // Hello apple

这里给出了三种正确的写法：

第一种写法索引字符串不添加任何引号，此时表示获取索引为字符串fruit的数组元素，输出apple。