PHP中max()函数和多维数组嵌套使用有哪些技巧？怎么实现？

gitbox 2025-06-16

1. 基本的max()函数使用

首先，我们回顾一下max()函数的基本用法。它可以接收一个数组或一组单独的数值作为参数，返回其中的最大值。例如：

<span><span><span class="hljs-variable">$values</span></span><span> = [</span><span><span class="hljs-number">10</span></span><span>, </span><span><span class="hljs-number">20</span></span><span>, </span><span><span class="hljs-number">30</span></span><span>, </span><span><span class="hljs-number">40</span></span><span>, </span><span><span class="hljs-number">50</span></span><span>];
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-title function_ invoke__">max</span></span><span>(</span><span><span class="hljs-variable">$values</span></span><span>);  </span><span><span class="hljs-comment">// 输出 50</span></span><span>
</span></span>

这个函数也支持多个参数传递，每个参数会被当作一个单独的值进行比较。例如：

<span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-title function_ invoke__">max</span></span><span>(</span><span><span class="hljs-number">10</span></span><span>, </span><span><span class="hljs-number">20</span></span><span>, </span><span><span class="hljs-number">30</span></span><span>, </span><span><span class="hljs-number">40</span></span><span>, </span><span><span class="hljs-number">50</span></span><span>);  </span><span><span class="hljs-comment">// 输出 50</span></span><span>
</span></span>

对于简单的数组结构来说，max()函数使用起来非常直接。但当数组变得更复杂，特别是多维数组时，情况就会有所不同。

2. 多维数组中的max()函数使用

在多维数组中，max()函数默认只能处理最外层的数组元素。如果我们希望在多维数组内部找到最大值，则需要借助一些额外的处理方法。以下是几种常见的技巧。

2.1 使用array_map和max结合

假设我们有一个多维数组，数组的每个子数组都包含了一些数字。如果我们想要获取每个子数组中的最大值，可以先通过array_map()函数将每个子数组应用max()，然后再使用max()找到最大的值。示例如下：

<span><span><span class="hljs-variable">$array</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-number">6</span></span><span>],
    [</span><span><span class="hljs-number">7</span></span><span>, </span><span><span class="hljs-number">8</span></span><span>, </span><span><span class="hljs-number">9</span></span><span>]
];

</span><span><span class="hljs-comment">// 获取每个子数组的最大值</span></span><span>
</span><span><span class="hljs-variable">$max_values</span></span><span> = </span><span><span class="hljs-title function_ invoke__">array_map</span></span><span>(</span><span><span class="hljs-string">'max'</span></span><span>, </span><span><span class="hljs-variable">$array</span></span><span>);

</span><span><span class="hljs-comment">// 输出每个子数组的最大值</span></span><span>
</span><span><span class="hljs-title function_ invoke__">print_r</span></span><span>(</span><span><span class="hljs-variable">$max_values</span></span><span>);  </span><span><span class="hljs-comment">// 输出 [3, 6, 9]</span></span><span>

</span><span><span class="hljs-comment">// 获取最大值</span></span><span>
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-title function_ invoke__">max</span></span><span>(</span><span><span class="hljs-variable">$max_values</span></span><span>);  </span><span><span class="hljs-comment">// 输出 9</span></span><span>
</span></span>

在这个例子中，array_map('max', $array)会应用max()函数到每个子数组上，得到每个子数组中的最大值。然后，再用max()函数获取这些最大值中的最大值。

2.2 使用array_column和max结合

有时候，多维数组中的数据是关联数组，每个子数组中有一个特定的键（如“score”），我们只想在某个特定键的值中找到最大值。在这种情况下，array_column()非常有用。它可以提取多维数组中所有子数组的某个指定列，然后与max()函数结合使用。示例如下：

<span><span><span class="hljs-variable">$array</span></span><span> = [
    [</span><span><span class="hljs-string">'name'</span></span><span> =&gt; </span><span><span class="hljs-string">'Alice'</span></span><span>, </span><span><span class="hljs-string">'score'</span></span><span> =&gt; </span><span><span class="hljs-number">85</span></span><span>],
    [</span><span><span class="hljs-string">'name'</span></span><span> =&gt; </span><span><span class="hljs-string">'Bob'</span></span><span>, </span><span><span class="hljs-string">'score'</span></span><span> =&gt; </span><span><span class="hljs-number">90</span></span><span>],
    [</span><span><span class="hljs-string">'name'</span></span><span> =&gt; </span><span><span class="hljs-string">'Charlie'</span></span><span>, </span><span><span class="hljs-string">'score'</span></span><span> =&gt; </span><span><span class="hljs-number">92</span></span><span>]
];

</span><span><span class="hljs-comment">// 提取所有学生的score值</span></span><span>
</span><span><span class="hljs-variable">$scores</span></span><span> = </span><span><span class="hljs-title function_ invoke__">array_column</span></span><span>(</span><span><span class="hljs-variable">$array</span></span><span>, </span><span><span class="hljs-string">'score'</span></span><span>);

</span><span><span class="hljs-comment">// 输出所有学生的分数</span></span><span>
</span><span><span class="hljs-title function_ invoke__">print_r</span></span><span>(</span><span><span class="hljs-variable">$scores</span></span><span>);  </span><span><span class="hljs-comment">// 输出 [85, 90, 92]</span></span><span>

</span><span><span class="hljs-comment">// 获取最大分数</span></span><span>
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-title function_ invoke__">max</span></span><span>(</span><span><span class="hljs-variable">$scores</span></span><span>);  </span><span><span class="hljs-comment">// 输出 92</span></span><span>
</span></span>

在这个例子中，array_column($array, 'score')提取了所有学生的分数，然后用max()函数找到最大分数。

2.3 嵌套多维数组的最大值

如果数组的嵌套层次更深，我们可以使用递归的方法来处理。递归函数可以用来遍历多维数组并找到最大值。以下是一个递归方法的示例：

<span><span><span class="hljs-function"><span class="hljs-keyword">function</span></span></span><span> </span><span><span class="hljs-title">getMaxValue</span></span><span>(</span><span><span class="hljs-params"><span class="hljs-variable">$array</span></span></span><span>) {
    </span><span><span class="hljs-variable">$max</span></span><span> = PHP_INT_MIN;  </span><span><span class="hljs-comment">// 设置一个初始值</span></span><span>

    </span><span><span class="hljs-keyword">foreach</span></span><span> (</span><span><span class="hljs-variable">$array</span></span><span> </span><span><span class="hljs-keyword">as</span></span><span> </span><span><span class="hljs-variable">$value</span></span><span>) {
        </span><span><span class="hljs-keyword">if</span></span><span> (</span><span><span class="hljs-title function_ invoke__">is_array</span></span><span>(</span><span><span class="hljs-variable">$value</span></span><span>)) {
            </span><span><span class="hljs-comment">// 如果值是一个数组，则递归调用</span></span><span>
            </span><span><span class="hljs-variable">$max</span></span><span> = </span><span><span class="hljs-title function_ invoke__">max</span></span><span>(</span><span><span class="hljs-variable">$max</span></span><span>, </span><span><span class="hljs-title function_ invoke__">getMaxValue</span></span><span>(</span><span><span class="hljs-variable">$value</span></span><span>));
        } </span><span><span class="hljs-keyword">else</span></span><span> {
            </span><span><span class="hljs-comment">// 否则直接与当前最大值比较</span></span><span>
            </span><span><span class="hljs-variable">$max</span></span><span> = </span><span><span class="hljs-title function_ invoke__">max</span></span><span>(</span><span><span class="hljs-variable">$max</span></span><span>, </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">$max</span></span><span>;
}

</span><span><span class="hljs-variable">$array</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-number">6</span></span><span>, [</span><span><span class="hljs-number">7</span></span><span>, </span><span><span class="hljs-number">8</span></span><span>]],
    </span><span><span class="hljs-number">9</span></span><span>
];

</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-title function_ invoke__">getMaxValue</span></span><span>(</span><span><span class="hljs-variable">$array</span></span><span>);  </span><span><span class="hljs-comment">// 输出 9</span></span><span>
</span></span>

此方法通过递归遍历数组的每一层，如果当前值是数组，则进入下一层继续比较；如果是数值，则与当前最大值进行比较。最终返回整个多维数组中的最大值。