php:關於變量，類型，作用域

判斷變數存在

<code><span>isset</span>(<span>$var</span>);<span>//只判断是否有这个变量，变量存在就是 TURE；</span></code>

判斷變數為空

<code>！empty(<span>$var</span>);<span>//</span>“”，<span>0</span>，“<span>0</span>”，<span>NULL</span>，<span>FALSE</span>，array(),var <span>$var</span>; 和没有任何属性的对象在用 empty判断时，都是空的，返回<span>TURE</span>；</code>

判斷是否為false

<code><span>if</span>(<span>0</span> == <span>false</span>){<span>echo</span><span>"true"</span>;}    <span>//true</span><span>if</span>(<span>0.0</span> == <span>false</span>){<span>echo</span><span>"true"</span>;}  <span>//true</span><span>if</span>(<span>array</span>() == <span>false</span>){<span>echo</span><span>"true"</span>;}  <span>//true</span><span>if</span>(<span>"0"</span> == <span>false</span>){<span>echo</span><span>"true"</span>;}  <span>//true</span><span>if</span>(<span>''</span> == <span>false</span>){<span>echo</span><span>"true"</span>;}   <span>//true</span><span>if</span>(<span>NULL</span> == <span>false</span>){<span>echo</span><span>"true"</span>;} <span>//true</span></code>

靜態變數:駐留記憶體的變數

<code><span><span>function</span><span>a</span><span>()</span>{</span><span>static</span><span>$a</span> = <span>1</span>;
    <span>echo</span><span>$a</span>;
    <span>$a</span>++;
}
a();<span>//1</span>
a();<span>//2</span></code>

隨的語言

<code><span><span>define</span></span>(<span>"TEST"</span>,<span>'codekissyoung'</span>);
echo TEST;<span>//codekissyoung</span></code>

將assoc 　數組拆解成變數

<code><span>$a</span> = <span>"test"</span>;
<span>$test</span> = <span>"i am the test"</span>;
<span><span>function</span><span>test</span>（）{</span><span>echo</span><span>"i am function test!"</span>;}   
<span>echo</span><span>$a</span>; <span>//test</span><span>echo</span><span>$$a</span>; <span>// i am the test</span><span>$a</span>(); <span>//i am function test!</span></code>

動態new 物件和呼叫函數

<code><span>foreach</span> (<span>$_POST</span><span>as</span><span>$key</span> => <span>$value</span>) {
            <span>$$key</span> = <span>$value</span>;
        ｝</code>

變數的參考

<code><span>//example.com?class=person&func=run</span><span>$class</span>=<span>$_GET</span>[<span>'class'</span>];
<span>$func</span>=<span>$_GET</span>[<span>'func'</span>];
<span>$obj</span>=<span>new</span><span>$class</span>();
<span>$obj</span>-><span>$func</span>();</code>

引用和函數結合使用全域名稱與使用全域版權聲明

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