PHP Foreach ループで配列キーを正しく取得する方法

Retrieving Array Keys in a Foreach Loop: Addressing an Error in Key Retrieval

In PHP, iterating over an array's values using a foreach loop can sometimes lead to unexpected behavior when accessing the keys. This is especially true if the array contains nested data structures.

Understanding the Error

Consider the following code:

<code class="php">foreach ($sampleArray as $item) {
    echo "&lt;tr&gt;&lt;td&gt;" . key($item) . "&lt;/td&gt;&lt;td&gt;" . $sampleArray['value1'] . "&lt;/td&gt;&lt;td&gt;" . $sampleArray['value2'] . "&lt;/td&gt;&lt;/tr&gt;";
}</code>

As illustrated in the provided question, this code will only output the key of the nested array (e.g., "value1"), not the desired key of the outer array itself (e.g., "4722").

Correcting the Issue

To retrieve the outer array key correctly, we need to modify the code slightly:

<code class="php">foreach ($sampleArray as $key => $item) {
    echo "&lt;tr&gt;&lt;td&gt;" . $key . "&lt;/td&gt;&lt;td&gt;" . $item['value1'] . "&lt;/td&gt;&lt;td&gt;" . $item['value2'] . "&lt;/td&gt;&lt;/tr&gt;";
}</code>

By adding a $key variable to the foreach loop, we can access the actual key of the outer array. This will then correctly print the desired key in the table.

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