What does << mean in php

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The operating environment of this tutorial: Windows 10 system, PHP version 7.1, DELL G3 computer.

What does

Bitwise operators refer to operations on binary bits aligned from low to high.

The two less-than signs "> means moving to the right. This We can understand bit operations more easily through an example:

<?php  
//定义权限  
define(&#39;READ&#39;, 1<< 0);    // 把可读权限放在最右边  
define(&#39;WRITE&#39;, 1<<1);    // 可读权限向左移一位  
define(&#39;EXCUTE&#39;, 1<<2);   // 可执行权限向左移两位  
   
//赋予权限  
$user_permission = READ | WRITE;  
   
//验证权限  
echo &#39;可读：&#39;, ($user_permission & READ) ? &#39;Yes&#39; : &#39;No&#39;, "\n";  
echo &#39;可写：&#39;, ($user_permission & WRITE) ? &#39;Yes&#39; : &#39;No&#39;, "\n";  
echo &#39;可执行：&#39;, ($user_permission & EXCUTE) ? &#39;Yes&#39; : &#39;No&#39;, "\n";  
?>

Output result:

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