laravel - Confused about php syntax?

Question

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As shown in the figure: method => function. what does this mean?

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Additional: Thank you everyone, my brain is rusty. . .

Answer 1

First of all, this is an array, and the key value of the array is the data calculated by these two functions

This is just a way to save trouble, no need to make a fuss

Answer 2

$this->username() returns the key name
trans returns the key value

Answer 3

Define array. . .
key is $this->username, value is trans('auth.failed')

Answer 4

Use the return value of the method $this->username() as the key

Answer 5

This is the assignment format in the PHP array, => the key in front and the value in the back. In this way, the errors array looks like this [username,trans(PalaPala)]