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How to understand this judgment expression ((DEBUG_MODE 2) == 2)_PHP tutorial
- WBOYOriginal
- 2016-07-13 10:51:401186browse
How to understand this judgment expression ((DEBUG_MODE & 2) == 2)
((DEBUG_MODE & 2) == 2)//If this sentence is to be true, it must be ((2 & 2)==2). How do you understand this formula?
define('DEBUG_MODE',false);//If yes 2, execution will display 1
if ((DEBUG_MODE & 2) == 2)
{
$smarty = '1';
}
else
{
$smarty= '0';
}
echo $smarty;
?>
Copy code [ ]
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"=&" What kind of operator is this?
$user =& init_users();
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It’s a reference, but I don’t know what the use of adding & in front of the function is.
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The AND operation in bit operations...
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Let me explain
In fact, the 2 here should be a fixed value, a constant that defines your mode. It will be easier to understand if you write it like this
define('MODE_A',2);
$now_mode = 2;
if(($now_mode & MODE_A) == MODE_A){
echo "The current mode is MODE_A";
}
?>
Copy the code. Some students said, why not use == to judge directly? In fact, there is another meaning here, which is the included relationship
For example, the value of 6 & 2 is 2, and the value of 6&3 is also 2, and 2 != 3
This method can often represent a range. Compare the relationship between IP and subnet mask in computer networks to understand
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Thank you LS, your answer is easy to understand.
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Original post posted by lmhllr on 2007-12-17 17:27 [url=http://www.111cn.cn/bbs/redirect.php?goto=findpost&pid=335104&ptid=46748]Link tag[img]http:// www.111cn.cn/bbs/images/common/back.gif[/img][/url]
The AND operation in bit operations...
Can you explain its function? I still don’t understand the purpose of writing this way.
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Original post by jayliu on 2007-12-17 16:55 [url=http://www.111cn.cn/bbs/redirect.php?goto=findpost&pid=335044&ptid=46748]Link tag[img]http:// www.111cn.cn/bbs/images/common/back.gif[/img][/url]
It’s a reference, but I don’t know what the use of adding & in front of the function is.
Added&
The function return value is a reference
PHP5 defaults to reference, and you cannot use & randomly. In PHP5, if the function directly returns false, the function with & will hang, and PHP will not be able to find the reference address
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I learned something new from LS. Thank you[img]http://www.111cn.cn/bbs/images/smilies/default/victory.gif[/img]
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So that’s it