php - checking previous with dynamic variable names

Looping through a dynamically-named array and comparing results to the previous positions results.

if($s>1 && $s<=10)
        {
            if( ${"strat{$s}"}[total] > ${"strat{$s-1}"}[total] )
                $sl_best = $sl_mult; //if this one did better than the previous one, then grab the value
        } 

And I'm getting error messages related the the ${"strat{$s-1}"}[total], specifically the {$s-1} portion. Here is the error message:

Parse error: syntax error, unexpected '-', expecting '}' ...

Any thoughts on how to check the previous array position on a dynamically named variable?

One solution I had was with 开发者_如何学JAVA$previous = $s-1; preceding every check and then substituting $strat[$previous] for ${"strat{$s-1}"}, but this seems ugly and I wanted to see if anyone had a better solution?

Dynamic variables should always be avoided, instead try using another array

Sample array

$strat = array(
  array('total' => 'some val'),
  array('total' => 'some val2'),
  array('total' => 'some val3'),
  array('total' => 'some val4'),
  ...
);

then

if($s>1 && $s<=10) {
  if($strat[$s]['total'] > $strat[$s-1]['total']) {
            $sl_best = $sl_mult; //if this one did better than the previous one, then grab the value
  } 
}