php array_merge、+、array_merge_r

概念不赘述，先看代码

<?php
    $arrayOne = [
          1     => 'a',
          'one' => 'b',
          2     => 'c',
          'two' => 'd'
    ];

    $arrayTwo = [
          0       => 'e',
          'one'   => 'f',
          1       => 'g',
          'three' => 'h'
    ];
    
    $merge      = array_merge($arrayOne, $arrayTwo);

    $plus       = $arrayOne + $arrayTwo;

    $recursive  = array_merge_recursive($arrayOne, $arrayTwo);

    print_r($merge);
    print_r($plus);
    print_r($recursive);

运行结果

Array
(
   [0] => a
   [one] => f
   [1] => c
   [two] => d
   [2] => e
   [3] => g
   [three] => h
)
Array
(
   [1] => a
   [one] => b
   [2] => c
   [two] => d
   [0] => e
   [three] => h
)
Array
(
   [0] => a
   [one] => Array
       (
           [0] => b
           [1] => f
       )
   [1] => c
   [two] => d
   [2] => e
   [3] => g
   [three] => h
)

概述一下，
array_merge。数字键，两数组均保留并从0开始重新排列键值；字符串键，键名不同时均保留，键名相同时保留第二个数组中值。
+。无论数字键名或字符串键名，键名不同时均保留，键名相同时保留第一个数组中值。
array_merge_recursive。数字键，两数组均保留并从0开始重新排列键值；字符串键，键名不同时均保留，键名相同时生成二维数组保留两数组中出现的值。