is_null

예

변수가 null인지 확인하십시오.

 <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 keyword">에코</span> <span class="token string double-quoted-string">"a is"</span> <span class="token operator">.</span> <span class="token function">IS_NULL</span> <span class="token punctuation">(</span> <span class="token variable">$ a</span> <span class="token punctuation">)</span> <span class="token operator">.</span> <span class="token string double-quoted-string">"<br>"</span> <span class="token punctuation">;</span>

<span class="token variable">$ b</span> <span class="token operator">=</span> <span class="token constant">null</span> <span class="token punctuation">;</span>
<span class="token keyword">에코</span> <span class="token string double-quoted-string">"B는"</span> <span class="token operator">.</span> <span class="token function">IS_NULL</span> <span class="token punctuation">(</span> <span class="token variable">$ B</span> <span class="token punctuation">)</span> <span class="token operator">.</span> <span class="token string double-quoted-string">"<br>"</span> <span class="token punctuation">;</span>

<span class="token variable">$ c</span> <span class="token operator">=</span> <span class="token string double-quoted-string">"null"</span> <span class="token punctuation">;</span>
<span class="token keyword">에코</span> <span class="token string double-quoted-string">"C는"</span> <span class="token operator">.</span> <span class="token function">IS_NULL</span> <span class="token punctuation">(</span> <span class="token variable">$ C</span> <span class="token punctuation">)</span> <span class="token operator">.</span> <span class="token string double-quoted-string">"<br>"</span> <span class="token punctuation">;</span>

<span class="token variable">$ d</span> <span class="token operator">=</span> <span class="token constant">null</span> <span class="token punctuation">;</span>
<span class="token keyword">Echo</span> <span class="token string double-quoted-string">"d is"</span> <span class="token operator">.</span> <span class="token function">IS_NULL</span> <span class="token punctuation">(</span> <span class="token variable">$ D</span> <span class="token punctuation">)</span> <span class="token operator">.</span> <span class="token string double-quoted-string">"<br>"</span> <span class="token punctuation">;</span>
<span class="token delimiter important">?></span></span>

직접 시도하십시오

예제 설명 :

변수 $ a의 값은 0이 아닌 0이므로 is_null ($ a)는 false를 반환합니다. 변수 $ B와 $ D의 값은 NULL이므로 IS_NULL ($ B) 및 IS_NULL ($ D) 모두 TRUE를 반환합니다. 변수 $ C의 값은 널이 아닌 문자열 "null"이므로 is_null ($ c)은 false를 반환합니다.