PHP遍历数组的方法汇总

<?php 
    $urls= array('aaa','bbb','c','ddd'); 
    foreach ($urls as $url){ 
      echo "This Site url is $url! <br />"; 
    } 
?> 

This Site url is aaa 
This Site url is bbb 
This Site url is c 
This Site url is ddd 

<?php 
    $urls= array('aaa','bbb','c','ddd'); 
    while(list($key,$val)= each($urls)) { 
      echo "This Site url is $val.<br />"; 
    } 
?> 

This Site url is aaa 
This Site url is bbb 
This Site url is c 
This Site url is ddd 

<?php 
    $urls= array('aaa','bbb','c','ddd'); 
    for ($i= 0;$i< count($urls); $i++){ 
      $str= $urls[$i]; 
      echo "This Site url is $str.<br />"; 
    } 
?> 

This Site url is aaa 
This Site url is bbb 
This Site url is c 
This Site url is ddd 

<?php 
  $arr= array(); 
  for($i= 0; $i< 50000; $i++){ 
  $arr[]= $irand(1000,9999); 
  } 
  function GetRunTime() 
  { 
  list($usec,$sec)=explode(" ",microtime()); 
  return ((float)$usec+(float)$sec); 
  } 
  ###################################### 
  $time_start= GetRunTime(); 
  for($i= 0; $i< count($arr); $i++){ 
  $str= $arr[$i]; 
  } 
  $time_end= GetRunTime(); 
  $time_used= $time_end- $time_start; 
  echo 'Used time of for:'.round($time_used, 7).'(s)<br /><br />'; 
  unset($str, $time_start, $time_end, $time_used); 
  ###################################### 
  $time_start= GetRunTime(); 
  while(list($key, $val)= each($arr)){ 
  $str= $val; 
  } 
  $time_end= GetRunTime(); 
  $time_used= $time_end- $time_start; 
  echo 'Used time of while:'.round($time_used, 7).'(s)<br /><br />'; 
  unset($str, $key, $val, $time_start, $time_end, $time_used); 
  ###################################### 
  $time_start= GetRunTime(); 
  foreach($arr as$key=> $val){ 
  $str= $val; 
  } 
  $time_end= GetRunTime(); 
  $time_used= $time_end- $time_start; 
  echo 'Used time of foreach:'.round($time_used, 7).'(s)<br /><br />'; 
  ?> 

Used time of for:0.0228429(s) 
Used time of while:0.0544658(s) 
Used time of foreach:0.0085628(s)