strtolower
將字符串轉化為小寫
把所有字符轉換為小寫:
<span class="token php language-php"><span class="token delimiter important"><?php</span> <span class="token keyword">echo</span> <span class="token function">strtolower</span> <span class="token punctuation">(</span> <span class="token string double-quoted-string">"Hello WORLD."</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token delimiter important">?></span></span>