for/while/foreach区别

<?php

echo 'for和while和foreach使用';

$arr=array(1,'a','hello');

for($i=0;$i<3;$i++){

echo $arr[i];

};

echo ' ','<hr>';

$j=0;

while($j<3){

echo $arr[$j];

$j++;

};

echo '<hr>';

foreach($arr as $key=>$value){

echo $key. '=>' . $value;

};

?>