php数组语法$ {让我很困惑

Question

I create a $values array and then extract the elements into local scope.

 $values['status'.$i] = $newStatus[$i];
 extract($values);

When I render an html page. I'm using the following

 <?php if(${'status'.$i} == 'OUT'){ ?>

but am confused by what the ${ is doing and why $status.$i won't resolve

Answer 1

$status.$i means

take value of $status variable and concatenate it with value of $i variable.

${'status'.$i} means

take value of $i variable, append id to 'status' string and take value of a variable 'status'.$i

Example:

With $i equals '2' and $status equals 'someStatus':

• $status.$i evaluated to 'someStatus' . '2', which is 'someStatus2'

• ${'status'.$i} evaluated to ${'status'.'2'} which is $status2. And if $status2 is defined variable - you will get some value.