php底层变量分析

<?php


//数组引用
$arr = array('a','b','c','d');
$x = & $arr[1];
$tmp = $arr;
$arr[1] = 'e';
echo $tmp[1];  //e

//数组指针
$arr = array('a','b','c','d');
foreach($arr as $key => $val){
}
var_dump(current($arr));  //boolean false

foreach($arr as $key => $val){
    $arr[$key]=$val;
}
var_dump(current($arr)); //b



/*Array
(
    [0] => a
    [1] => b
    [2] => c
    [3] => a
)
Array
(
    [0] => a
    [1] => b
    [2] => c
    [3] => b
)
Array
(
    [0] => a
    [1] => b
    [2] => c
    [3] => c
)
Array
(
    [0] => a
    [1] => b
    [2] => c
    [3] => c
)*/
foreach($arr as &$v){
}

foreach($arr as $v){
    print_r($arr);
}