<?php
   static $values  = array( 15.92, 53.27, 244.28, 388.46, 3.14, 2.92, 18.22, 4.03 );
   static $expected = 297.55;
   static $precision = 100; /* para não ter problemas com ponto flutuante */
 
   $target = floor( $expected * $precision );
   $len = count( $values );
   for( $i = 1; $i < pow( 2, $len ); $i++ ) {
      $soma = 0;
      $set = array();
      for( $j = 0; $j < $len; $j++ ) {
         if( 1 << $j & $i ) {
            $set[] = $j;
            $soma += floor( $values[$j] * $precision );
         }
      }
      if( $soma == $target ) {
         // Estamos exibindo na tela apenas como demonstração. Se preferir pode armazenar.
         foreach( $set as $pos ) echo "[$pos]{$values[$pos]} ";
         echo " = $expected\n";
      }
   }
?>

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