empty
檢查一個變量是否為空
中文(繁體)
中文(繁體)
檢查一個變量是否為空。同時檢查該變量是否已設置/聲明：
<span class="token php language-php"><span class="token delimiter important"><?php</span>
<span class="token variable">$a</span> <span class="token operator">=</span> <span class="token number">0</span> <span class="token punctuation">;</span>
<span class="token comment">// 結果為真，因為$a 是空的</span>
<span class="token keyword">if</span> <span class="token punctuation">(</span> <span class="token keyword">empty</span> <span class="token punctuation">(</span> <span class="token variable">$a</span> <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword">echo</span> <span class="token string double-quoted-string">"變量'a' 是空的。<br>"</span> <span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token comment">// 結果為真，因為$a 已設置</span>
<span class="token keyword">if</span> <span class="token punctuation">(</span> <span class="token keyword">isset</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 punctuation">{</span>
<span class="token keyword">echo</span> <span class="token string double-quoted-string">"變量'a' 已設置"</span> <span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token delimiter important">?></span></span>
var_export
is_integer
doubleval
strval
get_resource_id
unset
is_string
settype
