Comparison of several single-dimensional array traversal methods in PHP

The code is as follows:

<?php 
//a 
$arr=array(&#39;a&#39;=>&#39;abc&#39;,&#39;b&#39;=>123,&#39;c&#39;=>true); 
//b 
//$arr=range(&#39;a&#39;,&#39;d&#39;); 
//1 
for($i=0;$i<sizeof($arr);$i++) 
echo $arr[$i].&#39;, &#39;; 
echo &#39;<br />&#39;; 
//2 
foreach($arr as $key) 
echo "$key, "; 
echo &#39;<br />&#39;; 
//3 
foreach($arr as $key=>$val) 
echo "$key-$val, "; 
echo &#39;<br />&#39;; 
//4 
reset($arr); 
while($item=each($arr)){ 
echo $item[&#39;key&#39;].&#39;-&#39;.$item[&#39;value&#39;].&#39;, &#39;; 
} 
echo &#39;<br />&#39;; 
//5 
reset($arr); 
while(list($key,$val)=each($arr)){ 
echo "$key-$val, "; 
} 
echo &#39;<br />&#39;; 
?>

Use the statement a $arr=array('a'=>'abc','b'=>123,'c'=>true); to initialize $arr to get the number Index array, the output is as follows:
, , ,
abc, 123, 1,
a-abc, b-123, c-1,
a-abc, b-123, c-1,
a-abc, b- 123, c-1, use statement b $arr=range('a','d'); to initialize $arr to get the associative array, the output is as follows:
a, b, c, d,
a, b, c , d,
0-a, 1-b, 2-c, 3-d,
0-a, 1-b, 2-c, 3-d,
0-a, 1-b, 2-c, 3-d, the for loop only has limited numeric indexes; after the for and foreach traversal, the data does not need to be reset() to be available for the next traversal, while the each method does.