使用变量变量作为数组前缀

Question

Is it possible to use a variable variable as an array prefix? I have a set of arrays with the format $x_settings, and I want to output the values of just one depending on which prefix matches a condition.

This is an extremely stripped-down version of much more complex code, so thanks for your indulgence:

$current_env = 'local';

$local_settings = array
(
  'debug' => TRUE,
  'cake'  => TRUE,
  'death' => FALSE
);

$environments = array
(
  'local',
  'dev',
  'prod'
);

foreach( $environments as $env )
{
  if( $current_env == $env )
  {
    define('DEBUG', ${$env}_settings['debug']);
    define('CAKE', ${$env}_settings['cake']);
    define('DEATH', ${$env}_settings['death']);

    break;
  }
}

As you can see I tried using ${$env}_settings[] but that gave me a PHP error:

unexpected '_settings' (T_STRING)

Possible?

Answer 1

Yes, it is possible. Your loop should look like below:

foreach( $environments as $env )
{
  if( $current_env == $env )
  {
    define('DEBUG', ${$env.'_settings'}['debug']);
    define('CAKE',  ${$env.'_settings'}['cake']);
    define('DEATH', ${$env.'_settings'}['death']);
    break;
  }
}

Notes:

• I've fixed the typo in your array declaration. You were using just = instead of =>.
• I've added a break inside your loop - otherwise, you'll be trying to re-declare constants and that will cause PHP to output errors
• I've changed = to ==. = is the assignment operator. You need to use == (loose comparison) or === (strict comparison) instead.

Demo