array_filter函數的基本用法和參數都有哪些？詳細解析如何正確使用array_filter

gitbox 2025-07-26

在PHP中， array_filter函數是一個非常實用的工具，它用於過濾數組中的元素，基於給定的回調函數返回的布爾值來決定是否保留該元素。這個函數常常被用於從數組中剔除不符合條件的元素，或者基於某些邏輯提取數據。

基本語法

<span><span><span class="hljs-title function_ invoke__">array_filter</span></span><span>(</span><span><span class="hljs-keyword">array</span></span><span> </span><span><span class="hljs-variable">$array</span></span><span>, ?</span><span><span class="hljs-keyword">callable</span></span><span> </span><span><span class="hljs-variable">$callback</span></span><span> = </span><span><span class="hljs-literal">null</span></span><span>, </span><span><span class="hljs-keyword">int</span></span><span> </span><span><span class="hljs-variable">$mode</span></span><span> = </span><span><span class="hljs-number">0</span></span><span>): </span><span><span class="hljs-keyword">array</span></span><span>
</span></span>

參數說明：

array (必需)
這是你想要進行過濾操作的數組。
callback (可選)
這是一個回調函數，用於判斷數組的每個元素是否滿足某個條件。如果該參數被設置為null ， array_filter將會去除數組中的所有“空”值，如false , null , 0 , 空字符串等。
mode (可選)
這是一個常量，用於決定如何使用回調函數來判斷數組元素。常用的模式有：
- ARRAY_FILTER_USE_KEY ：回調函數接收數組的鍵而不是值。
- ARRAY_FILTER_USE_BOTH ：回調函數同時接收鍵和值。

基本用法

下面是一些常見的array_filter使用示例：

示例1：過濾掉數組中的“空”值

<span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-variable">$arr</span></span><span> = [</span><span><span class="hljs-number">0</span></span><span>, </span><span><span class="hljs-number">1</span></span><span>, </span><span><span class="hljs-literal">false</span></span><span>, </span><span><span class="hljs-number">2</span></span><span>, </span><span><span class="hljs-literal">null</span></span><span>, </span><span><span class="hljs-number">3</span></span><span>, </span><span><span class="hljs-string">'apple'</span></span><span>, </span><span><span class="hljs-string">''</span></span><span>, </span><span><span class="hljs-number">4</span></span><span>];

</span><span><span class="hljs-variable">$result</span></span><span> = </span><span><span class="hljs-title function_ invoke__">array_filter</span></span><span>(</span><span><span class="hljs-variable">$arr</span></span><span>);
</span><span><span class="hljs-title function_ invoke__">print_r</span></span><span>(</span><span><span class="hljs-variable">$result</span></span><span>);
</span><span><span class="hljs-meta">?&gt;</span></span><span>
</span></span>

輸出：

 <span><span>Array
(
    [</span><span><span class="hljs-meta">1</span></span><span>] =&gt; </span><span><span class="hljs-number">1</span></span><span>
    [</span><span><span class="hljs-meta">3</span></span><span>] =&gt; </span><span><span class="hljs-number">2</span></span><span>
    [</span><span><span class="hljs-meta">5</span></span><span>] =&gt; </span><span><span class="hljs-number">3</span></span><span>
    [</span><span><span class="hljs-meta">6</span></span><span>] =&gt; apple
    [</span><span><span class="hljs-meta">8</span></span><span>] =&gt; </span><span><span class="hljs-number">4</span></span><span>
)
</span></span>

在這個示例中， array_filter過濾掉了所有值為false 、 null 、 0 、空字符串等“空”值。

示例2：使用回調函數過濾數組

<span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-variable">$arr</span></span><span> = [</span><span><span class="hljs-number">1</span></span><span>, </span><span><span class="hljs-number">2</span></span><span>, </span><span><span class="hljs-number">3</span></span><span>, </span><span><span class="hljs-number">4</span></span><span>, </span><span><span class="hljs-number">5</span></span><span>];

</span><span><span class="hljs-variable">$result</span></span><span> = </span><span><span class="hljs-title function_ invoke__">array_filter</span></span><span>(</span><span><span class="hljs-variable">$arr</span></span><span>, function(</span><span><span class="hljs-variable">$value</span></span><span>) {
    </span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-variable">$value</span></span><span> % </span><span><span class="hljs-number">2</span></span><span> == </span><span><span class="hljs-number">0</span></span><span>; </span><span><span class="hljs-comment">// 只保留偶數</span></span><span>
});

</span><span><span class="hljs-title function_ invoke__">print_r</span></span><span>(</span><span><span class="hljs-variable">$result</span></span><span>);
</span><span><span class="hljs-meta">?&gt;</span></span><span>
</span></span>

輸出：

 <span><span>Array
(
    [</span><span><span class="hljs-meta">1</span></span><span>] =&gt; </span><span><span class="hljs-number">2</span></span><span>
    [</span><span><span class="hljs-meta">3</span></span><span>] =&gt; </span><span><span class="hljs-number">4</span></span><span>
)
</span></span>

在這個例子中， array_filter使用一個回調函數來檢查數組中的每個元素是否是偶數，返回值為true時，元素就會被保留。

示例3：使用ARRAY_FILTER_USE_KEY根據鍵過濾

<span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-variable">$arr</span></span><span> = [
    </span><span><span class="hljs-string">'first'</span></span><span> =&gt; </span><span><span class="hljs-number">1</span></span><span>,
    </span><span><span class="hljs-string">'second'</span></span><span> =&gt; </span><span><span class="hljs-number">2</span></span><span>,
    </span><span><span class="hljs-string">'third'</span></span><span> =&gt; </span><span><span class="hljs-number">3</span></span><span>,
    </span><span><span class="hljs-string">'fourth'</span></span><span> =&gt; </span><span><span class="hljs-number">4</span></span><span>
];

</span><span><span class="hljs-variable">$result</span></span><span> = </span><span><span class="hljs-title function_ invoke__">array_filter</span></span><span>(</span><span><span class="hljs-variable">$arr</span></span><span>, function(</span><span><span class="hljs-variable">$key</span></span><span>) {
    </span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-title function_ invoke__">strpos</span></span><span>(</span><span><span class="hljs-variable">$key</span></span><span>, </span><span><span class="hljs-string">'t'</span></span><span>) === </span><span><span class="hljs-number">0</span></span><span>; </span><span><span class="hljs-comment">// 只保留鍵以't'開頭的元素</span></span><span>
}, ARRAY_FILTER_USE_KEY);

</span><span><span class="hljs-title function_ invoke__">print_r</span></span><span>(</span><span><span class="hljs-variable">$result</span></span><span>);
</span><span><span class="hljs-meta">?&gt;</span></span><span>
</span></span>

輸出：

 <span><span>Array
(
    [</span><span><span class="hljs-meta">third</span></span><span>] =&gt; </span><span><span class="hljs-number">3</span></span><span>
    [</span><span><span class="hljs-meta">fourth</span></span><span>] =&gt; </span><span><span class="hljs-number">4</span></span><span>
)
</span></span>

這個例子演示瞭如何根據數組鍵進行過濾， ARRAY_FILTER_USE_KEY讓回調函數接收數組的鍵而不是值。

示例4：使用ARRAY_FILTER_USE_BOTH同時使用鍵和值

<span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-variable">$arr</span></span><span> = [
    </span><span><span class="hljs-string">'apple'</span></span><span> =&gt; </span><span><span class="hljs-number">5</span></span><span>,
    </span><span><span class="hljs-string">'banana'</span></span><span> =&gt; </span><span><span class="hljs-number">0</span></span><span>,
    </span><span><span class="hljs-string">'orange'</span></span><span> =&gt; </span><span><span class="hljs-number">2</span></span><span>,
    </span><span><span class="hljs-string">'grape'</span></span><span> =&gt; </span><span><span class="hljs-number">3</span></span><span>
];

</span><span><span class="hljs-variable">$result</span></span><span> = </span><span><span class="hljs-title function_ invoke__">array_filter</span></span><span>(</span><span><span class="hljs-variable">$arr</span></span><span>, function(</span><span><span class="hljs-variable">$value</span></span><span>, </span><span><span class="hljs-variable">$key</span></span><span>) {
    </span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-variable">$value</span></span><span> &gt; </span><span><span class="hljs-number">1</span></span><span> &amp;&amp; </span><span><span class="hljs-title function_ invoke__">strpos</span></span><span>(</span><span><span class="hljs-variable">$key</span></span><span>, </span><span><span class="hljs-string">'a'</span></span><span>) !== </span><span><span class="hljs-literal">false</span></span><span>; </span><span><span class="hljs-comment">// 保留值大於1且鍵中包含'a'的元素</span></span><span>
}, ARRAY_FILTER_USE_BOTH);

</span><span><span class="hljs-title function_ invoke__">print_r</span></span><span>(</span><span><span class="hljs-variable">$result</span></span><span>);
</span><span><span class="hljs-meta">?&gt;</span></span><span>
</span></span>

輸出：

 <span><span>Array
(
    [</span><span><span class="hljs-meta">apple</span></span><span>] =&gt; </span><span><span class="hljs-number">5</span></span><span>
    [</span><span><span class="hljs-meta">orange</span></span><span>] =&gt; </span><span><span class="hljs-number">2</span></span><span>
)
</span></span>

此示例使用ARRAY_FILTER_USE_BOTH ，讓回調函數同時使用鍵和值進行過濾操作。結果會保留值大於1且鍵中包含字母'a' 的元素。

注意事項

回調函數的返回值：
回調函數的返回值必須是布爾值true或false 。如果返回true ，則該元素會被保留，返回false時則會被剔除。
性能考慮：
array_filter會遍歷整個數組進行檢查。如果數組非常大，且回調函數很複雜，可能會影響性能。在這種情況下，考慮是否可以優化回調函數，或者使用其他方法。
鍵的保持：
array_filter在過濾時會保持原始數組的鍵。這意味著如果你從數組中剔除了元素，結果數組中的鍵將不會重新索引。

結論

array_filter是一個非常強大的函數，可以用來根據各種條件過濾數組中的元素。它不僅支持基本的過濾操作，還提供了靈活的回調函數和多種模式，能夠幫助你在處理數據時更加高效。理解和正確使用array_filter可以讓你的代碼更加簡潔和高效，尤其是在處理大規模數據或需要特定過濾條件的場景中。

相關標籤:
array_filter

array_filter