array

当合并的数组是，数值键名相同时，array_merge()、array_merge_recursive()不会覆盖，+是前盖后；

 JAVA
    [1] => PHP
    [2] => PYTHON
    [3] => PHP
    [4] => C++
    [5] => PYTHON
    [6] => PHP
)
Array
(
    [0] => JAVA
    [1] => PHP
    [2] => PYTHON
    [3] => PHP
    [4] => C++
    [5] => PYTHON
    [6] => PHP
)
Array
(
    [0] => JAVA
    [1] => PHP
    [2] => PHP
)

键名各不相同时，array_merge()、+、array_merge_recursive()不会覆盖。

#键名不同
$a1=array('a'=>"1",'b'=>"2");
$a2=array('c'=>"3",'d'=>"4");
$a3=array('e'=>"5",'f'=>"6");
print_r(array_merge($a1,$a2,$a3));
print_r(array_merge_recursive($a1,$a2,$a3));
print_r($a1+$a2+$a3)

#结果相同
Array
(
    [a] => 1
    [b] => 2
    [c] => 3
    [d] => 4
    [e] => 5
    [f] => 6
)

存在键名相同时，array_merge()后边值覆盖前面的值，+是前盖后，array_merge_recursive() 不会进行键名覆盖，而是将多个相同键名的值递归组成一个数组；

$a1=array('a'=>"1",'b'=>"2");
$a2=array('a'=>"3",'d'=>"4");
$a3=array('a'=>"5",'f'=>"6");
print_r(array_merge($a1,$a2,$a3));
print_r(array_merge_recursive($a1,$a2,$a3));
print_r($a1+$a2+$a3);

#结果
Array
(
    [a] => 5
    [b] => 2
    [d] => 4
    [f] => 6
)
Array
(
    [a] => Array
        (
            [0] => 1
            [1] => 3
            [2] => 5
        )

    [b] => 2
    [d] => 4
    [f] => 6
)
Array
(
    [a] => 1
    [b] => 2
    [d] => 4
    [f] => 6
)