php生成器简介和示例

<?php
    function xrange($start, $limit, $step = 1) {
        if ($start < $limit) {
            if ($step <= 0) {
                throw new LogicException('step必须是正数');
            }
            for ($i = $start; $i <= $limit; $i += $step) {
                yield $i;
            }
        } else {
            if ($step >= 0) {
                throw new LogicException('step必须是负数');
            }
            for ($i = $start; $i >= $limit; $i += $step) {
                yield $i;
            }
        }
    }
    /* 注意range() 和 xrange() 的结果在下面的统一输出中. */
    echo '来自range()的单个奇数: ';
    foreach (range(1, 9, 2) as $number) {
        echo "$number ";
    }
    echo "\n";
    echo '来自xrange()的单个奇数 ';
    foreach (xrange(1, 9, 2) as $number) {
        echo "$number ";
    }
?>

Single digit odd numbers from range():  1 3 5 7 9 
Single digit odd numbers from xrange(): 1 3 5 7 9