Analysis of the difference between PHP merge array + and array_merge

The main difference is that if the same key name appears in two or more arrays, the key name is divided into a string or a number. Please note that

1) When the key name is a number, array_merge() will not overwrite it. Remove the original value, but + merge the array will return the first value as the final result, and "discard" those values ​​​​with the same key name in the subsequent arrays (not overwrite)

2) When the key name is a character, + still returns the first value as the final result, and "discards" those values ​​in the subsequent arrays with the same key name, but array_merge() will overwrite the previous values ​​with the same key name. Value

It should be noted that the array key form 'number' is equivalent to a number

$a = array('a','b'); 
$b = array('c', 'd'); 
$c = $a + $b; 
var_dump($a); 
var_dump(array_merge($a, $b)); 

$a = array(0 => 'a', 1 => 'b'); 
$b = array(0 => 'c', 1 => 'b'); 
$c = $a + $b; 
var_dump($c); 
var_dump(array_merge($a, $b)); 

$a = array('a', 'b'); 
$b = array('0' => 'c', 1 => 'b'); 
$c = $a + $b; 
var_dump($c); 
var_dump(array_merge($a, $b)); 

$a = array(0 => 'a', 1 => 'b'); 
$b = array('0' => 'c', '1' => 'b'); 
$c = $a + $b; 
var_dump($c); 
var_dump(array_merge($a, $b));

Result

array 
0 => string 'a' (length=1) 
1 => string 'b' (length=1) 
2 => string 'c' (length=1) 
3 => string 'd' (length=1) 

array 
0 => string 'a' (length=1) 
1 => string 'b' (length=1) 

array 
0 => string 'a' (length=1) 
1 => string 'b' (length=1) 
2 => string 'c' (length=1) 
3 => string 'b' (length=1) 

array 
0 => string 'a' (length=1) 
1 => string 'b' (length=1) 

array 
0 => string 'a' (length=1) 
1 => string 'b' (length=1) 
2 => string 'c' (length=1) 
3 => string 'b' (length=1) 

array 
0 => string 'a' (length=1) 
1 => string 'b' (length=1) 

array 
0 => string 'a' (length=1) 
1 => string 'b' (length=1) 
2 => string 'c' (length=1) 
3 => string 'b' (length=1)

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