与“ for”循环相比,“ foreach”比较慢。foreach复制需要在其上执行迭代的数组。
为了提高性能,需要使用引用的概念。除此之外,“ foreach”易于使用。
以下是一个简单的代码示例-
<?php $my_arr = array(); for ($i = 0; $i < 10000; $i++) { $my_arr[] = $i; } $start = microtime(true); foreach ($my_arr as $k => $v) { $my_arr[$k] = $v + 1; } echo "This completed in ", microtime(true) - $start, " seconds"; echo "<br>"; $start = microtime(true); foreach ($my_arr as $k => &$v) { $v = $v + 1; } echo "This completed in ", microtime(true) - $start, " seconds"; echo "<br>"; $start = microtime(true); foreach ($my_arr as $k => $v) {} echo "This completed in ", microtime(true) - $start, " seconds"; echo "<br>"; $start = microtime(true); foreach ($my_arr as $k => &$v) {} echo "This completed in ", microtime(true) - $start, " seconds"; ?>
输出结果
这将产生以下输出-
This completed in 0.00058293342590332 seconds This completed in 0.00063300132751465 seconds This completed in 0.00023412704467773 seconds This completed in 0.00026583671569824 seconds