怎麼用array_keys 避免數組中鍵重複的錯誤？ PHP 新手常見問題

gitbox 2025-09-11

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<h1>怎麼用 array_keys 避免數組中鍵重複的錯誤？PHP 新手常見問題</h1>

<p>在 PHP 中，數組是非常靈活的數據結構，可以同時存儲鍵與值。然而，新手經常會遇到的一個問題是：當你在數組中不小心定義了重複的鍵，後定義的值會覆蓋掉之前的值，導致數據丟失或邏輯錯誤。</p>

<h2>數組鍵重複的常見情況</h2>
<p>舉個簡單的例子：</p>

<pre><code </span><span><span class="hljs-class"><span class="hljs-keyword">class</span></span></span><span>="</span><span><span class="hljs-title">language</span></span><span>-</span><span><span class="hljs-title">php</span></span><span>">
$</span><span><span class="hljs-title">data</span></span><span> = [
    "</span><span><span class="hljs-title">id</span></span><span>" => 1,
    "</span><span><span class="hljs-title">name</span></span><span>" => "</span><span><span class="hljs-title">Alice</span></span><span>",
    "</span><span><span class="hljs-title">id</span></span><span>" => 2
];

</span><span><span class="hljs-title">print_r</span></span><span>($</span><span><span class="hljs-title">data</span></span><span>);
</</span><span><span class="hljs-title">code</span></span><span>></</span><span><span class="hljs-title">pre</span></span><span>>

<</span><span><span class="hljs-title">p</span></span><span>>運行後，數組中只會保留最後一次的 <</span><span><span class="hljs-title">code</span></span><span>>"</span><span><span class="hljs-title">id</span></span><span>" => 2</</span><span><span class="hljs-title">code</span></span><span>>，而第一次定義的 <</span><span><span class="hljs-title">code</span></span><span>>"</span><span><span class="hljs-title">id</span></span><span>" => 1</</span><span><span class="hljs-title">code</span></span><span>> 已經被覆蓋掉。</</span><span><span class="hljs-title">p</span></span><span>>

<</span><span><span class="hljs-title">h2</span></span><span>>如何使用 </span><span><span class="hljs-title">array_keys</span></span><span> 檢查重複鍵？</</span><span><span class="hljs-title">h2</span></span><span>>
<</span><span><span class="hljs-title">p</span></span><span>><</span><span><span class="hljs-title">code</span></span><span>></span><span><span class="hljs-title">array_keys</span></span><span>()</</span><span><span class="hljs-title">code</span></span><span>> 函數可以返回數組中所有鍵組成的新數組，我們可以通過它來檢測是否有重複的鍵。</</span><span><span class="hljs-title">p</span></span><span>>

<</span><span><span class="hljs-title">pre</span></span><span>><</span><span><span class="hljs-title">code</span></span><span> </span><span><span class="hljs-title">class</span></span><span>="</span><span><span class="hljs-title">language</span></span><span>-</span><span><span class="hljs-title">php</span></span><span>">
$</span><span><span class="hljs-title">data</span></span><span> = [
    "</span><span><span class="hljs-title">id</span></span><span>" => 1,
    "</span><span><span class="hljs-title">name</span></span><span>" => "</span><span><span class="hljs-title">Alice</span></span><span>",
    "</span><span><span class="hljs-title">id</span></span><span>" => 2
];

$</span><span><span class="hljs-title">keys</span></span><span> = </span><span><span class="hljs-title">array_keys</span></span><span>($</span><span><span class="hljs-title">data</span></span><span>);

// 統計鍵的出現次數
$</span><span><span class="hljs-title">keyCounts</span></span><span> = </span><span><span class="hljs-title">array_count_values</span></span><span>($</span><span><span class="hljs-title">keys</span></span><span>);

// 找出重複的鍵
$</span><span><span class="hljs-title">duplicates</span></span><span> = </span><span><span class="hljs-title">array_filter</span></span><span>($</span><span><span class="hljs-title">keyCounts</span></span><span>, </span><span><span class="hljs-title">function</span></span><span>($</span><span><span class="hljs-title">count</span></span><span>) {
    </span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-variable">$count</span></span><span> > </span><span><span class="hljs-number">1</span></span><span>;
});

</span><span><span class="hljs-keyword">if</span></span><span> (!</span><span><span class="hljs-keyword">empty</span></span><span>(</span><span><span class="hljs-variable">$duplicates</span></span><span>)) {
    </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"發現重複的鍵: "</span></span><span> . </span><span><span class="hljs-title function_ invoke__">implode</span></span><span>(</span><span><span class="hljs-string">", "</span></span><span>, </span><span><span class="hljs-title function_ invoke__">array_keys</span></span><span>(</span><span><span class="hljs-variable">$duplicates</span></span><span>));
} </span><span><span class="hljs-keyword">else</span></span><span> {
    </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"沒有發現重複鍵"</span></span><span>;
}

通過這種方式，我們可以在程序邏輯中快速發現重複鍵的問題，避免後續出現數據覆蓋。

更推薦的做法

在定義數組時，保持鍵名唯一性。
如果鍵名來源於動態數據，使用array_keys檢查並提前處理。
必要時結合array_unique對鍵或值進行去重。

總結

PHP 新手容易忽略數組鍵的覆蓋問題，但利用array_keys等函數，就能在編碼過程中提前發現並避免錯誤。良好的習慣是：在寫代碼時對數組結構保持清晰，並在需要時做檢查，這樣可以大大減少調試的成本。

相關標籤:
array_keys