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 4

string 'b' (length=1)

array

  'r' => int 5

  0 => int 6

  1 => int 7

  2 => int 8

string '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