Just getting started with PHP, ask an operator in the $a++,++ $a, $a--,--$a, the problem

$a=21;$b=$a++;    $c=++$a;     echo $a;    echo $b;    echo $c;    

I understand the results were 23, 22, 23,

But why is the result of the input 23,21,23 solved?

Reply content:

$a=21;$b=$a++;    $c=++$a;     echo $a;    echo $b;    echo $c;    

I understand the results were 23, 22, 23,

But why is the result of the input 23,21,23 solved?

This is not a problem with PHP, the program language is the same. $a++is the first to do the operation and then self-increment, ++$a is the first self-increment and then do the operation

+ + Pre-set the first self-increment after the reset
The specific disassembly is equivalent to the following:

$a = 21;//$b = $a++;$b = $a;    $a++;//$c = ++$a;++$a;$c = $a;  

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