這次帶給大家php雙引號中訪問數組元素報錯如何處理，php雙引號中訪問數組元素報錯處理的注意事項有哪些，下面就是實戰案例，一起來看一下。
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>";
}結果竟報如下錯誤訊息：
#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
從錯誤訊息看是單引號的問題，果斷去掉之後就沒報錯了。然而我就納悶了，引用下標為字串的陣列元素難道不該加引號嗎？到php官方手冊去查了關於數組的描述，有一段是這樣的：
$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']";這裡給了兩種錯誤的寫法，當一個普通數組變數或超全局數組變數包含在雙引號中時，引用索引為字串的陣列元素，索引字串不應該再添加單引號。那正確的寫法是怎麼樣的呢？於是我繼續找官方手冊，找到如下說法：
$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 here
print "Hello $arr[fruit]"; // Hello apple
// With one exception: braces surrounding arrays within strings allows constants
// to be interpreted
print "Hello {$arr[fruit]}"; // Hello carrot
print "Hello {$arr['fruit']}"; // Hello apple這裡給了三種正確的寫法：
##第一種寫法索引字串不添加任何引號，此時表示取得索引為字串fruit的陣列元素，輸出apple。
第二種寫法索引字串也沒有添加任何引號，同時將數組變數用一對花括號{ }給包了起來，此時fruit實際上表示一個常數，而不是一個字串，因此表示取得索引為fruit常數值的陣列元素，常數fruit的值是veggie,所以輸出carrot。
第三種寫法是引用字串不僅添加了單引號，同時也將數組變數用一對花括號{ }給包了起來，此時表示取得索引為字串fruit的陣列元素，輸出apple。
後來我繼續找，發現這樣一段程式碼：// Incorrect. This works but also throws a PHP error of level E_NOTICE because // of an undefined constant named fruit // // Notice: Use of undefined constant fruit - assumed 'fruit' in... print $arr[fruit]; // apple <pre name="code" class="php">print $arr['fruit']; // apple
// This defines a constant to demonstrate what's going on. The value 'veggie'// is assigned to a constant named fruit.define('fruit', 'veggie');// Notice the difference nowprint $arr[fruit]; // carrot
print $arr['fruit']; // apple結論：
#1. 陣列變數未以雙引號包含時，
(1) 索引字串加上單引號表示字串本身<pre name="code" class="php">$arr['fruit']
$arr[fruit]
2. 陣列變數以雙引號包含時，
(1) 索引字串不加單引號表示字串本身"$arr[fruit]"
"{$arr[fruit]}"<pre name="code" class="php"><pre name="code" class="php">"{$arr['fruit']}"(4) 索引字串加上單引號且陣列變數未加上花括號，為錯誤寫法，報錯：Parse error: parse error, expecting T_STRING' or T_VARIABLE' or T_NUM_STRING'
<pre name="code" class="php"><pre name="code" class="php">"$arr['fruit']"
php手冊數組說明URL
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