blocks|key|4051337|text|我觉得你想要的不是|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4051338|<?php+if($this->id+!=+Session::get('id')+&&+$this->id+!=+NULL):+?>
++<a+href="<?php+echo+Config::get('URL');+?>messages/compose/<?php+echo+System::escape($this->user->user_id);+?>"+class="btn+btn-block+btn-success"><i+class="fa+fa-envelope-alt">Send+message</a>|code-block|syntax|javascript|4051339|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I think you want the and not the or

<pre><code>&lt;?php if($this-&gt;id != Session::get('id') &amp;&amp; $this-&gt;id != NULL): ?&gt;
 &lt;a href="&lt;?php echo Config::get('URL'); ?&gt;messages/compose/&lt;?php echo System::escape($this-&gt;user-&gt;user_id); ?&gt;" class="btn btn-block btn-success"&gt;&lt;i class="fa fa-envelope-alt"&gt;&lt;/i&gt;Send message&lt;/a&gt;
</code></pre>

blocks|key|3770895|text|我用&&而不是%7C%7C解决了这个问题|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3770896|<?php+if($this->id+!=+Session::get('id')+&&+$this->id+!=+NULL):+?>
++++++<a+href="<?php+echo+Config::get('URL');+?>messages/compose/<?php+echo+System::escape($this->user->user_id);+?>"+class="btn+btn-block+btn-success"><i+class="fa+fa-envelope-alt">Send+message</a>
<?php+endif;+?>|code-block|syntax|javascript|3770897|我不想接受一个简短的答案，下面是关于AND和OR语句的一些信息|3770898|和OR算子|BOLD|3770899|如果第一个条件和第二个条件都为真，AND运算符将显示一个记录。
如果第一个条件或第二个条件为真，则OR运算符将显示记录。|blockquote|3770900|和运算符示例|3770901|以下SQL语句在"+customers“表中选择来自”德国“和”柏林“的所有客户：|3770902|SELECT+*+FROM+Customers
WHERE+Country='Germany'
AND+City='Berlin';|3770903|或算子示例|3770904|以下SQL语句在"+customers“表中从城市”柏林“或"München”中选择所有客户：|3770905|SELECT+*+FROM+Customers
WHERE+City='Berlin'
OR+City='München';|3770906|组合与OR语句|3770907|还可以组合AND和OR+(使用括号形成复杂表达式)。
以下SQL语句在"+customers“表中选择来自”德国“的所有客户，城市必须与”柏林“或"München”相等：|3770908|SELECT+*+FROM+Customers
++++WHERE+Country='Germany'
++++AND+(City='Berlin'+OR+City='München');|3770909|entityMap^0|2|2|7|2|0|0|I|3|M|2|0|0|5|0|0|0|6|0|0|0|0|5|0|0|0|0|7|0|0|0^^$0|@$1|2|3|4|5|6|7|1C|8|@$9|1D|A|1E|B|C]|$9|1F|A|1G|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|1H|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1I|8|@$9|1J|A|1K|B|C]|$9|1L|A|1M|B|C]]|D|@]|E|$]]|$1|M|3|N|5|6|7|1N|8|@$9|1O|A|1P|B|O]]|D|@]|E|$]]|$1|P|3|Q|5|R|7|1Q|8|@]|D|@]|E|$]]|$1|S|3|T|5|6|7|1R|8|@$9|1S|A|1T|B|O]]|D|@]|E|$]]|$1|U|3|V|5|R|7|1U|8|@]|D|@]|E|$]]|$1|W|3|X|5|H|7|1V|8|@]|D|@]|E|$I|J]]|$1|Y|3|Z|5|6|7|1W|8|@$9|1X|A|1Y|B|O]]|D|@]|E|$]]|$1|10|3|11|5|R|7|1Z|8|@]|D|@]|E|$]]|$1|12|3|13|5|H|7|20|8|@]|D|@]|E|$I|J]]|$1|14|3|15|5|6|7|21|8|@$9|22|A|23|B|O]]|D|@]|E|$]]|$1|16|3|17|5|R|7|24|8|@]|D|@]|E|$]]|$1|18|3|19|5|H|7|25|8|@]|D|@]|E|$I|J]]|$1|1A|3|-4|5|6|7|26|8|@]|D|@]|E|$]]]|1B|$]]

I fixed this problem by using <code>&amp;&amp;</code> instead of <code>||</code>

<pre><code>&lt;?php if($this-&gt;id != Session::get('id') &amp;&amp; $this-&gt;id != NULL): ?&gt;
 &lt;a href="&lt;?php echo Config::get('URL'); ?&gt;messages/compose/&lt;?php echo System::escape($this-&gt;user-&gt;user_id); ?&gt;" class="btn btn-block btn-success"&gt;&lt;i class="fa fa-envelope-alt"&gt;&lt;/i&gt;Send message&lt;/a&gt;
&lt;?php endif; ?&gt;
</code></pre>

I don't want to accept a short answer so here's some information about <code>AND</code> and <code>OR</code> statements

AND and OR operator

<blockquote>
 The AND operator displays a record if both the first condition AND the
 second condition are true.
 
 The OR operator displays a record if either the first condition OR the
 second condition is true.
</blockquote>

AND operator example

<blockquote>
 The following SQL statement selects all customers from the country
 "Germany" AND the city "Berlin", in the "Customers" table:
</blockquote>

<pre><code>SELECT * FROM Customers
WHERE Country='Germany'
AND City='Berlin';
</code></pre>

OR operator example

<blockquote>
 The following SQL statement selects all customers from the city
 "Berlin" OR "München", in the "Customers" table:
</blockquote>

<pre><code>SELECT * FROM Customers
WHERE City='Berlin'
OR City='München';
</code></pre>

Combining AND and OR statements

<blockquote>
 You can also combine AND and OR (use parenthesis to form complex
 expressions).
 
 The following SQL statement selects all customers from the country
 "Germany" AND the city must be equal to "Berlin" OR "München", in the
 "Customers" table:
</blockquote>

<pre><code>SELECT * FROM Customers
 WHERE Country='Germany'
 AND (City='Berlin' OR City='München');
</code></pre>

I have a variable which its value is NULL I am trying to only show a button if their ID doesn't match a variable or if the variable is not null, here's my script:

<pre><code>&lt;?php if($this-&gt;id != Session::get('id') || $this-&gt;id != NULL): ?&gt;
 &lt;a href="&lt;?php echo Config::get('URL'); ?&gt;messages/compose/&lt;?php echo System::escape($this-&gt;user-&gt;user_id); ?&gt;" class="btn btn-block btn-success"&gt;&lt;i class="fa fa-envelope-alt"&gt;&lt;/i&gt;Send message&lt;/a&gt;
&lt;?php endif; ?&gt;
</code></pre>

No matter what, the href is still being shown, I have tried <code>is_null</code>, <code>empty</code>, <code>!isset()</code>, I <code>var_dump</code> the variable, which comes back with <code>NULL</code> hence it shouldn't show the a href, but low and behold it's still showing it.

Using if statement for a null variable which is not running correctly

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我有一个变量，其值为null，如果它们的ID与变量不匹配，或者变量不是NULL，则只显示一个按钮，下面是我的脚本：<?php if($this->id != Session::get('id') || $this->id != NULL): ?> <a href="<?php echo Config::get...

问对未正确运行的空变量使用if语句
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问对未正确运行的空变量使用if语句EN