php数组合并用加号和用array_merge()的区别

php数组合并用加号和用array_merge()的区别

第一先看数组元素:

<?php$a = array('r'=>1,2,3,4);var_dump('a',$a);$b = array('r'=>5,6,7,8);var_dump('b',$b);$c = array('r'=>5,6,7,8,9);var_dump('c',$c);
var_dump('a+b',$a+$b);var_dump('a+c', $a+$c);
var_dump('amb', array_merge($a, $b));var_dump('amc', array_merge($a, $c));

第二看输出:

string 'a' (length=1)array
'r' => int 1
0 => int 2
1 => int 3
2 => int 4string 'b' (length=1)array
'r' => int 5
0 => int 6
1 => int 7
2 => int 8string 'c' (length=1)array
'r' => int 5
0 => int 6
1 => int 7
2 => int 8
3 => int 9
string 'a+b' (length=3)array
'r' => int 1
0 => int 2
1 => int 3
2 => int 4
string 'a+c' (length=3)array
'r' => int 1
0 => int 2
1 => int 3
2 => int 4
3 => int 9
string 'amb' (length=3)array
'r' => int 5
0 => int 2
1 => int 3
2 => int 4
3 => int 6
4 => int 7
5 => int 8
string 'amc' (length=3)array
'r' => int 5
0 => int 2
1 => int 3
2 => int 4
3 => int 6
4 => int 7
5 => int 8
6 => int 9

结论:用加号合并数组:既考虑数字索引的键值对,也考虑字符串索引的键值对,用前边数组的值覆盖后边的键名相同的值;
用array_merge()合并数组:只考虑字符串索引的键值对,用后边数组的值覆盖掉前面数组中键名相同的值,数字索引的值则不覆盖,同时保留
另外:array_merge()会重排两个数组的数字索引,"+"则不会