php学习代码杂记

16/2/22

赋值运算

<span>1</span><span>$a</span> = "cmflovehxc"<span>;</span><span>2</span><span>$b</span>=<span>$a</span><span>;</span><span>3</span><span>$c</span>=&<span>$a</span><span>;</span><span>4</span><span>$a</span> = "cmflovehxc"<span>;</span><span>5</span><span>6</span><span>echo</span><span>$b</span>."<br />"<span>;</span><span>7</span><span>echo</span><span>$c</span>;

(1)“=”：把右边表达式的值赋给左边的运算数。它将右边表达式值复制一份，交给左边的运算数。换而言之，首先给左边的运算数申请了一块内存，然后把复制的值放到这个内存中。

相当于JS的等于号。变量赋值；两个变量是两个不同的堆内存。

(2)“=&”：引用赋值，意味着两个变量都指向同一个数据。它将使两个变量共享一块内存，如果这个内存存储的数据变了，那么两个变量的值都会发生变化。

两个变量是两个相同的堆内存。

常量

<span> 1</span><span>define</span>("PI1",3.14<span>);</span><span> 2</span><span>$p</span> = "PI1"<span>;</span><span> 3</span><span>echo</span><span>$p</span>;<span>//</span><span>PI1</span><span> 4</span><span>echo<strong style="color:transparent">9来源gaodai#ma#com搞@代~码$网</strong>搞gaodaima代码</span><span>constant</span>(<span>$p</span>);<span>//</span><span>3.14</span><span> 5</span><span>if</span>(<span>defined</span>(<span>$p</span>)==<span>true</span><span>){</span><span> 6</span><span>echo</span> '111'<span>  ; </span><span> 7</span> }<span>else</span><span>{</span><span> 8</span><span>echo</span> '222'<span>;</span><span> 9</span><span>}</span><span>10</span><span>//</span><span>返回111<br />11 //constant（）与defined（）都有一种翻译功能<br /></span>

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