max()函數與數組映射（array_map）結合使用的最佳實踐，如何提高效率？

提高效率的思路

優化的關鍵在於。如果我們只是為了得到最大值，並不需要完整的映射結果，就可以將邏輯寫在一次循環中完成：

 <span><span><span class="hljs-variable">$prices</span></span><span> = [</span><span><span class="hljs-number">1999</span></span><span>, </span><span><span class="hljs-number">2500</span></span><span>, </span><span><span class="hljs-number">3200</span></span><span>, </span><span><span class="hljs-number">1800</span></span><span>];

</span><span><span class="hljs-variable">$maxPrice</span></span><span> = </span><span><span class="hljs-literal">null</span></span><span>;
</span><span><span class="hljs-keyword">foreach</span></span><span> (</span><span><span class="hljs-variable">$prices</span></span><span> </span><span><span class="hljs-keyword">as</span></span><span> </span><span><span class="hljs-variable">$p</span></span><span>) {
    </span><span><span class="hljs-variable">$converted</span></span><span> = </span><span><span class="hljs-variable">$p</span></span><span> / </span><span><span class="hljs-number">100</span></span><span>;
    </span><span><span class="hljs-keyword">if</span></span><span> (</span><span><span class="hljs-variable">$maxPrice</span></span><span> === </span><span><span class="hljs-literal">null</span></span><span> || </span><span><span class="hljs-variable">$converted</span></span><span> &gt; </span><span><span class="hljs-variable">$maxPrice</span></span><span>) {
        </span><span><span class="hljs-variable">$maxPrice</span></span><span> = </span><span><span class="hljs-variable">$converted</span></span><span>;
    }
}

</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-variable">$maxPrice</span></span><span>; </span><span><span class="hljs-comment">// 輸出 32</span></span><span>
</span></span>

這樣做避免了array_map創建新數組的過程，節省了內存，並且在大數據場景下性能會更好。

結合匿名函數與生成器

如果代碼需要保留函數式風格，又想減少內存消耗，可以考慮生成器：

 <span><span><span class="hljs-function"><span class="hljs-keyword">function</span></span></span><span> </span><span><span class="hljs-title">convertPrices</span></span><span>(</span><span><span class="hljs-params"><span class="hljs-variable">$prices</span></span></span><span>) {
    </span><span><span class="hljs-keyword">foreach</span></span><span> (</span><span><span class="hljs-variable">$prices</span></span><span> </span><span><span class="hljs-keyword">as</span></span><span> </span><span><span class="hljs-variable">$p</span></span><span>) {
        </span><span><span class="hljs-keyword">yield</span></span><span> </span><span><span class="hljs-variable">$p</span></span><span> / </span><span><span class="hljs-number">100</span></span><span>;
    }
}

</span><span><span class="hljs-variable">$prices</span></span><span> = [</span><span><span class="hljs-number">1999</span></span><span>, </span><span><span class="hljs-number">2500</span></span><span>, </span><span><span class="hljs-number">3200</span></span><span>, </span><span><span class="hljs-number">1800</span></span><span>];

</span><span><span class="hljs-variable">$maxPrice</span></span><span> = </span><span><span class="hljs-title function_ invoke__">max</span></span><span>(</span><span><span class="hljs-title function_ invoke__">iterator_to_array</span></span><span>(</span><span><span class="hljs-title function_ invoke__">convertPrices</span></span><span>(</span><span><span class="hljs-variable">$prices</span></span><span>)));

</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-variable">$maxPrice</span></span><span>; </span><span><span class="hljs-comment">// 輸出 32</span></span><span>
</span></span>

雖然這裡使用了iterator_to_array ，但在更複雜的流式處理場景中，生成器可以避免大規模數據一次性加載進內存，具有更好的擴展性。

• 相關標籤:

  array_map