PHP中array_merge()和array1+array2的区别分析

2019-10-31 16:44:59 Albin Wong 1731

在PHP中使用`array_merge()`和`array1+array2`的方式进行数组合并操作时，但两者效果并不相同

###  当两个数组都为索引数组时

- 使用`array_merge()`函数进行数组合并时，其键名从 0 开始进行重新索引
- 使用`array1+array2`进行数组合并时，出现相同键名的值，后面键名相同的会被抛弃

```php
	$array1 = array(1 => 2, 2 => 4);
	$array2 = array(2 => 3, 3 => 5);
	```

---

使用`array_merge()`函数输出

```php
	Array
	(
		[0] => 2
		[1] => 4
		[2] => 3
		[3] => 5
	)
	```

---
	使用`array1+array2`时输出

```php
	Array
	(
		[1] => 2
		[2] => 4
		[3] => 5
	)
	```

###  当两个数组都为关联数组时

- 使用`array_merge()`函数进行数组合并操作，出现键名相同时，后面数组元素值会覆盖前面数组元素值
- 使用`array1+array2`进行数组合并时，出现相同键名的值，后面相同数组元素值会被抛弃

```php
	$array1 = array("color" => "red", "shape" => "circle");
	$array2 = array("shape" => "trapezoid", "color" => "gray");
	```
	---
	使用`array_merge()`函数输出
	```php
	Array
	(
		[color] => gray
		[shape] => trapezoid
	)
	```
	---
	使用`array1+array2`时输出
	```
	Array
	(
		[color] => red
		[shape] => circle
	)
	```
---
### 当两个数组中，键名既有索引又有关联
- 使用`array_merge()`函数进行数组合并操作，出现相同索引键名时，其键名以 0 开始进行重新索引；出现相同关联键名时，后面数组元素值会覆盖前面数组元素值
- 使用`array1+array2`进行数组合并操作，出现相同键名的值，后面相同数组元素值会被抛弃

```php
	$array1 = array("color" => "red", 1 => 2, 4);
	$array2 = array("a", "b", "color" => "gray", "shape" => "trapezoid", 6);
	```
	---
	使用`array_merge()`函数输出
	```php
	Array
	(
		[color] => gray
		[0] => 2
		[1] => 4
		[2] => a
		[3] => b
		[shape] => trapezoid
		[4] => 6
	)
	```
	---
	使用`array1+array2`时输出
	```php
	Array
	(
		[color] => red
		[1] => 2
		[2] => 4
		[0] => a
		[shape] => trapezoid
	)
	```

<div style="color:red;">如果两个数组中，有一个为空数组，输出结果无区别</div>

### 递归地合并一个或多个数组 array_merge_recursive()
- `array_merge()`与 `array_merge_recursive()` 函数之间的不同是在处理两个或更多个数组元素有相同的键名的情况。`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。
- 将一个或多个数组的单元合并起来，一个数组中的值附加在前一个数组的后面。返回作为结果的数组。
- 如果输入的数组中有相同的字符串键名，则这些值会被合并到一个数组中去，这将递归下去，因此如果一个值本身是一个数组，本函数将按照相应的条目把它合并为另一个数组。需要注意的是，如果数组具有相同的数值键名，后一个值将不会覆盖原来的值，而是附加到后面。

```php
	$array1 = array("color" => array("favorite" => "red"), 5);
	$array2 = array(10, "color" => array("favorite" => "green", "blue"));
	print_r(array_merge_recursive($array1, $array2));
	```
	---
	以上例程会输出：
	```php
	Array
	(
		[color] => Array
			(
				[favorite] => Array
					(
						[0] => red
						[1] => green
					)
				[0] => blue
			)
		[0] => 5
		[1] => 10
	)
	```

(3) Comments

John Doe- Reply

February 26, 2013 at 1:18 pm
- saqib sarwar- Reply
  
  February 26, 2013 at 1:20 pm
  
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John Doe- Reply

February 26, 2013 at 1:27 pm

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PHP中array_merge()和array1+array2的区别分析

(3) Comments

John Doe- Reply

saqib sarwar- Reply

John Doe- Reply

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