is_countable

实例

检查一个变量的内容是否是可计数的值：

<span class="token php language-php"><span class="token delimiter important"><?php</span>
<span class="token variable">$a</span> <span class="token operator">=</span> <span class="token string double-quoted-string">"Hello"</span><span class="token punctuation">;</span>
<span class="token keyword">echo</span> <span class="token string double-quoted-string">"a is "</span> <span class="token operator">.</span> <span class="token function">is_countable</span><span class="token punctuation">(</span><span class="token variable">$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">$b</span> <span class="token operator">=</span> <span class="token keyword">array</span><span class="token punctuation">(</span><span class="token string double-quoted-string">"red"</span><span class="token punctuation">,</span> <span class="token string double-quoted-string">"green"</span><span class="token punctuation">,</span> <span class="token string double-quoted-string">"blue"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">echo</span> <span class="token string double-quoted-string">"b is "</span> <span class="token operator">.</span> <span class="token function">is_countable</span><span class="token punctuation">(</span><span class="token variable">$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">$c</span> <span class="token operator">=</span> <span class="token keyword">array</span><span class="token punctuation">(</span><span class="token string double-quoted-string">"Peter"</span><span class="token operator">=></span><span class="token string double-quoted-string">"35"</span><span class="token punctuation">,</span> <span class="token string double-quoted-string">"Ben"</span><span class="token operator">=></span><span class="token string double-quoted-string">"37"</span><span class="token punctuation">,</span> <span class="token string double-quoted-string">"Joe"</span><span class="token operator">=></span><span class="token string double-quoted-string">"43"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">echo</span> <span class="token string double-quoted-string">"c is "</span> <span class="token operator">.</span> <span class="token function">is_countable</span><span class="token punctuation">(</span><span class="token variable">$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">$d</span> <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token keyword">echo</span> <span class="token string double-quoted-string">"d is "</span> <span class="token operator">.</span> <span class="token function">is_countable</span><span class="token punctuation">(</span><span class="token variable">$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>

亲自试一试

例子解释：

变量 $a 包含一个字符串，它不是一个可计数的值，所以 is_countable($a) 将返回 FALSE。而变量 $b、$c 和 $d 包含的是数组，它们是可计数的值，所以 is_countable($b)、is_countable($c) 和 is_countable($d) 都将返回 TRUE。数组无论是索引数组还是关联数组，都是可计数的。