PHP 中怎麼用ord() 函數來判斷一個字符是大寫還是小寫？

<span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-comment">// 這裡是與文章內容無關的PHP代碼示例</span></span><span>
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"這是一個示例程序，用於演示PHP代碼結構。"</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">/*
 * 文章標題：PHP 中怎麼用 ord() 函數來判斷一個字符是大寫還是小寫？
 *
 * ord() 函數的作用是返回字符的 ASCII 值。
 * 在ASCII碼表中，大寫字母 A-Z 的範圍是 65 到 90，
 * 小寫字母 a-z 的範圍是 97 到 122。
 * 使用 ord() 函數獲取字符的 ASCII 碼，
 * 就可以通過比較這個數值來判斷字符是大寫還是小寫。
 */</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">$ascii</span></span><span> &lt;= </span><span><span class="hljs-number">90</span></span><span>) {
        </span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-string">"大寫字母"</span></span><span>;
    } </span><span><span class="hljs-keyword">elseif</span></span><span> (</span><span><span class="hljs-variable">$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">"小寫字母"</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">// 測試示例</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">/*
輸出結果：
字符 'A' 是：大寫字母
字符 'z' 是：小寫字母
字符 'M' 是：大寫字母
字符 'm' 是：小寫字母
字符 '9' 是：不是英文字母
字符 '@' 是：不是英文字母
*/</span>

<span class="hljs-comment">/*
總結：
ord() 函數非常適合用於判斷字符類型，尤其是英文字符的大小寫判斷。
只需獲取字符的 ASCII 编碼，然後根據ASCII碼范围做判断即可。
*/</span>
</span><span><span class="hljs-meta">?&gt;</span></span><span>
</span></span>