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<code>while ($i = 'AAA' && $j = 'BBB') { var_dump($i, $j); sleep(3); } </code>
<code class="php">输出结果 bool(true) string(3) "BBB"</code>
<code> ------------------------------------------------------------- 在写一个后台监听程序的时候使用了while循环,于是纠结了一下`while`中的条件表达式</code>
For the above code, I expected to output AAA BBB, but why is it true BBB
Look at this code
<code>while($ret = 100) { var_dump($ret) // output:100 }</code>
How does the conditional expression $ret=100
in the brackets here result in true
or false
. What I want is to first assign the value 100
to the $ret
variable, and then perform a Boolean conversion on $ret
to get the result.
Hope everyone can help clear up the confusion. Thank you.
<code>while ($i = 'AAA' && $j = 'BBB') { var_dump($i, $j); sleep(3); } </code>
<code class="php">输出结果 bool(true) string(3) "BBB"</code>
<code> ------------------------------------------------------------- 在写一个后台监听程序的时候使用了while循环,于是纠结了一下`while`中的条件表达式</code>
For the above code, I expected to output AAA BBB, but why is it true BBB
Look at this code
<code>while($ret = 100) { var_dump($ret) // output:100 }</code>
How does the conditional expression $ret=100
in the brackets here result in true
or false
. What I want is to first assign the value 100
to the $ret
variable, and then perform a Boolean conversion on $ret
to get the result.
Hope everyone can help clear up the confusion. Thank you.
<code>if (($i = 'AAA') && ($j = 'BBB')) { var_dump($i, $j); } </code>
Attention &&
Priority
Operator logic problem, price brackets are wrong
<code class="php">while (($i = 'AAA') && ( $j = 'BBB')) { var_dump($i, $j);// true bbbbb sleep(3); }</code>
The comma operator causes the output bbb, V=1,2. At this time, v is 2
2. An infinite loop. Convert to boolea can be ret = ret && true