PHP 中怎么用 ord() 函数来判断一个字符是大写还是小写？

<span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-comment">// 这里是与文章内容无关的PHP代码示例</span></span><span>
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"这是一个示例程序，用于演示PHP代码结构。"</span></span><span>;
</span><span><span class="hljs-meta">?&gt;</span></span><span>

&lt;hr&gt;

</span><span><span class="hljs-meta">&lt;?php</span></span><span>
<span class="hljs-comment">/*
 * 文章标题：PHP 中怎么用 ord() 函数来判断一个字符是大写还是小写？
 *
 * ord() 函数的作用是返回字符的 ASCII 值。
 * 在ASCII码表中，大写字母 A-Z 的范围是 65 到 90，
 * 小写字母 a-z 的范围是 97 到 122。
 * 利用 ord() 函数获取字符的 ASCII 码，
 * 就可以通过比较这个数值来判断字符是大写还是小写。
 */</span>

</span><span><span class="hljs-function"><span class="hljs-keyword">function</span></span></span><span> </span><span><span class="hljs-title">checkCase</span></span><span>(</span><span><span class="hljs-params"><span class="hljs-variable">$char</span></span></span><span>) {
    </span><span><span class="hljs-variable">$ascii</span></span><span> = </span><span><span class="hljs-title function_ invoke__">ord</span></span><span>(</span><span><span class="hljs-variable">$char</span></span><span>);
    </span><span><span class="hljs-keyword">if</span></span><span> (</span><span><span class="hljs-variable">$ascii</span></span><span> &gt;= </span><span><span class="hljs-number">65</span></span><span> &amp;&amp; </span><span><span class="hljs-variable">$ascii</span></span><span> &lt;= </span><span><span class="hljs-number">90</span></span><span>) {
        </span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-string">"大写字母"</span></span><span>;
    } </span><span><span class="hljs-keyword">elseif</span></span><span> (</span><span><span class="hljs-variable">$ascii</span></span><span> &gt;= </span><span><span class="hljs-number">97</span></span><span> &amp;&amp; </span><span><span class="hljs-variable">$ascii</span></span><span> &lt;= </span><span><span class="hljs-number">122</span></span><span>) {
        </span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-string">"小写字母"</span></span><span>;
    } </span><span><span class="hljs-keyword">else</span></span><span> {
        </span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-string">"不是英文字母"</span></span><span>;
    }
}

</span><span><span class="hljs-comment">// 测试示例</span></span><span>
</span><span><span class="hljs-variable">$testChars</span></span><span> = [</span><span><span class="hljs-string">'A'</span></span><span>, </span><span><span class="hljs-string">'z'</span></span><span>, </span><span><span class="hljs-string">'M'</span></span><span>, </span><span><span class="hljs-string">'m'</span></span><span>, </span><span><span class="hljs-string">'9'</span></span><span>, </span><span><span class="hljs-string">'@'</span></span><span>];

</span><span><span class="hljs-keyword">foreach</span></span><span> (</span><span><span class="hljs-variable">$testChars</span></span><span> </span><span><span class="hljs-keyword">as</span></span><span> </span><span><span class="hljs-variable">$c</span></span><span>) {
    </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"字符 '<span class="hljs-subst">{$c}</span></span></span><span>' 是：" . </span><span><span class="hljs-title function_ invoke__">checkCase</span></span><span>(</span><span><span class="hljs-variable">$c</span></span><span>) . </span><span><span class="hljs-string">"&lt;br&gt;"</span></span><span>;
}

<span class="hljs-comment">/*
输出结果：
字符 'A' 是：大写字母
字符 'z' 是：小写字母
字符 'M' 是：大写字母
字符 'm' 是：小写字母
字符 '9' 是：不是英文字母
字符 '@' 是：不是英文字母
*/</span>

<span class="hljs-comment">/*
总结：
ord() 函数非常适合用于判断字符类型，尤其是英文字符的大小写判断。
只需获取字符的 ASCII 编码，然后根据ASCII码范围做判断即可。
*/</span>
</span><span><span class="hljs-meta">?&gt;</span></span><span>
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