unset

例

変数を破壊する：

 <span class="token php language-php"><span class="token delimiter important"><？php</span>  
<span class="token variable">$ a</span> <span class="token operator">=</span> <span class="token string double-quoted-string">"hello world！"</span> <span class="token punctuation">;</span>  
<span class="token keyword">ECHO</span> <span class="token string double-quoted-string">「以前の変数 &#39;A&#39;： "の値を削除します</span><span class="token operator">。</span> <span class="token variable">$ a</span> <span class="token operator">。</span> <span class="token string double-quoted-string">"<br>"</span> <span class="token punctuation">;</span>  
<span class="token keyword">Unset</span> <span class="token punctuation">（</span> <span class="token variable">$ a</span> <span class="token punctuation">）</span> <span class="token punctuation">;</span>  
<span class="token keyword">echo</span> <span class="token string double-quoted-string">"削除後の変数 &#39;a&#39;の値："</span> <span class="token operator">。</span> <span class="token variable">$ a</span> <span class="token punctuation">;</span>  
<span class="token delimiter important">？></span></span>

自分で試してみてください