is_null

Example

Check if the variable is NULL:

 <span class="token php language-php"><span class="token delimiter important"><?php</span>
<span class="token variable">$a</span> <span class="token operator">=</span> <span class="token number">0</span> <span class="token punctuation">;</span>
<span class="token keyword">echo</span> <span class="token string double-quoted-string">"a is "</span> <span class="token operator">.</span> <span class="token function">is_null</span> <span class="token punctuation">(</span> <span class="token variable">$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">$b</span> <span class="token operator">=</span> <span class="token constant">null</span> <span class="token punctuation">;</span>
<span class="token keyword">echo</span> <span class="token string double-quoted-string">"b is "</span> <span class="token operator">.</span> <span class="token function">is_null</span> <span class="token punctuation">(</span> <span class="token variable">$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">$c</span> <span class="token operator">=</span> <span class="token string double-quoted-string">"null"</span> <span class="token punctuation">;</span>
<span class="token keyword">echo</span> <span class="token string double-quoted-string">"c is "</span> <span class="token operator">.</span> <span class="token function">is_null</span> <span class="token punctuation">(</span> <span class="token variable">$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>

Try it yourself

Example explanation:

The value of the variable $a is 0, not NULL, so is_null($a) returns FALSE. The values of the variables $b and $d are NULL, so both is_null($b) and is_null($d) return TRUE. The value of the variable $c is a string "null", not NULL, so is_null($c) returns FALSE.