How to merge arrays in PHP

Two methods and differences of array merging in PHP are introduced. Friends in need can refer to the following

Two methods and differences of PHP array merging
If it is an associative array, as follows:

Copy code The code is as follows:

$a = array(
'where' => 'uid=1',
'order' => 'uid',
);
$b = array(
'where' => 'uid=2',
'order' => 'uid desc',
);

1. array_merge, if two arrays have the same key, the latter one will overwrite the previous one

Copy code The code is as follows:

$c = array_merge($a, $b);
var_export($c);//The result is the same as The original $b is the same
$d = array_merge($b, $a);
var_export($d);//The result is the same as the original $a

2. "+" operator, if two arrays have the same key, the former one will overwrite the latter

Copy code The code is as follows:

$c = $a + $b;
var_export($c);//The result is the same as the original $a
$d = $b + $a;
var_export($d);//The result is the same as the original $b

If it is a numeric index array, as follows:

Copy code The code is as follows:

$a = array(
1 => '1111111',
2 => '222222222'
);
$b = array(
4 => '33333333333',
1 => '444444444'
);

1. array_merge. The effect is similar to the code foreach each array element, and then push each element into a new stack

Copy code The code is as follows:

< ;?php
$c = array_merge($a, $b);
var_export($c);
$d = array_merge($b, $a);
var_export($d) ;

Output:
array (
0 => '1111111',
1 => '222222222',
2 => ' 33333333333',
3 => '444444444',
)
array (
0 => '33333333333',
1 => '444444444',
2 = > '1111111',
3 => '222222222',
)
2. "+" operator. The effect is similar to the code foreach each array element, and then push each element into a new In the stack, if the same key already exists, it will not be processed

Copy code The code is as follows:

$c = $a + $b;
var_export($c);
$d = $b + $a;
var_export($d);

Output :
array (
1 => '1111111',
2 => '222222222',
4 => '33333333333',
)
array (
4 => '33333333333',
1 => '444444444',
2 => '222222222',
)

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