is_finite
判断是否为有限值
<span class="token php language-php"><span class="token delimiter important"><?php</span> <span class="token keyword">echo</span> <span class="token function">is_finite</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">echo</span> <span class="token function">is_finite</span><span class="token punctuation">(</span><span class="token function">log</span><span class="token punctuation">(</span><span class="token number">0</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 function">is_finite</span><span class="token punctuation">(</span><span class="token number">2000</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token delimiter important">?></span></span>