PHP FOR vs FOREACH性能比较

“foreach”比“for”慢。foreach复制需要执行迭代的数组。为了提高性能,需要使用引用的概念。除此之外,“foreach”也很容易使用。

例子

<?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";
?>

结果

This completed in 0.00058293342590332 seconds
This completed in 0.00063300132751465 seconds
This completed in 0.00023412704467773 seconds
This completed in 0.00026583671569824 seconds
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