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This article introduces the knowledge of "what is the result of connecting an array with a + sign in PHP". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

What is the result of concatenating arrays with a + sign in PHP?

In our development, we sometimes combine two numbers and connect them together. At this time, we should be careful not to be lazy and use the + sign directly. Why? Let's look at the following code:

$a = [1,2]

B = [4, 5, 6]

$c = $a + $b

Print_r ($c)

Please tell me directly what the result is with the first one. Maybe if I ask you this, you should be able to guess, the result is:

Array

(

[0] = > 1

[1] = > 2

[2] = > 6

)

As you can see, the array connected by the + operator turns out to be a union. That is, according to the key, the same key will not be overwritten, and no key will be added to form a new array. It's not really adding up the two arrays.

What if we use $baked rooma? The result is the content of $b.

$c = $b + $a

Print_r ($c)

Array

(

[0] = > 4

[1] = > 5

[2] = > 6

)

So what are we going to do if we get an array of 1, 2, 4, 5, 6? Yes, using the array_merge () function, notice the location of the array Key:

C = array_merge ($a, $b)

Print_r ($c)

Array

(

[0] = > 1

[1] = > 2

[2] = > 4

[3] = > 5

[4] = > 6

)

C = array_merge ($b, $a)

Print_r ($c)

Array

(

[0] = > 4

[1] = > 5

[2] = > 6

[3] = > 1

[4] = > 2

)

What if it's a Hash array in the form of key/value? The result is the same, no keys in $a will be merged, and the same keys will not be processed.

$a = ['a'= > 1,'b' = > 2]

B = ['a'= > 4,'b'= > 5,'c'= > 6]

Print_r ($astatb)

Array

(

[a] = > 1

[B] = > 2

[C] = > 6

)

C = array_merge ($a, $b)

Print_r ($c)

C = array_merge ($b, $a)

Print_r ($c)

Array

(

[a] = > 1

[B] = > 2

[C] = > 6

)

Array

(

[a] = > 4

[B] = > 5

[C] = > 6

)

Array

(

[a] = > 1

[B] = > 2

[C] = > 6

)

For the above Hash array, the result of using the array_merge () function is the same as using the + sign, because they still compare the keys. So the merged array will not add content, if it is undefined subscript, it will be added directly as a numeric subscript.

Finally, let's try again. Connection of operator:

C = $a. $b

Print_r ($c)

ArrayArray

Well, it doesn't make any sense for strings that are forcibly converted to string to be concatenated.

Test code: https://github.com/zhangyue0503/dev-blog/blob/master/php/201911/source/PHP%E4%B8%AD%E7%94%A8%2B%E5%8F%B7%E8%BF%9E%E6%8E%A5%E6%95%B0%E7%BB%84%E7%9A%84%E7%BB%93%E6%9E%9C%E6%98%AF%EF%BC%9F.php

Reference document: https://www.php.net/manual/zh/language.operators.array.php

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