PHP5.5新特性之yield理解与用法实例分析

/** * 计算平方数列 * @param $start * @param $stop * @return Generator */function squares($start, $stop) {  if ($start < $stop) {    for ($i = $start; $i <= $stop; $i++) {      yield $i => $i * $i;    }  }  else {    for ($i = $start; $i >= $stop; $i--) {      yield $i => $i * $i; //迭代生成数组： 键=》值    }  }}foreach (squares(3, 15) as $n => $square) {  echo $n . 'squared is' . $square . '<br>';}

//对某一数组进行加权处理$numbers = array('nike' => 200, 'jordan' => 500, 'adiads' => 800);//通常方法，如果是百万级别的访问量，这种方法会占用极大内存function rand_weight($numbers){  $total = 0;  foreach ($numbers as $number => $weight) {    $total += $weight;    $distribution[$number] = $total;  }  $rand = mt_rand(0, $total-1);  foreach ($distribution as $num => $weight) {    if ($rand < $weight) return $num;  }}//改用yield生成器function mt_rand_weight($numbers) {  $total = 0;  foreach ($numbers as $number => $weight) {    $total += $weight;    yield $number => $total;  }}function mt_rand_generator($numbers){  $total = array_sum($numbers);  $rand = mt_rand(0, $total -1);  foreach (mt_rand_weight($numbers) as $num => $weight) {    if ($rand < $weight) return $num;  }}