Emitted when an array has a key more than once
<?php
$arr = [
'a' => 'one',
'b' => 'two',
'c' => 'this text will be overwritten by the next line',
'c' => 'three',
];This can be caused by variadic arguments if @no-named-arguments is not specified:
<?php
function foo($bar, ...$baz): array
{
return [$bar, ...$baz]; // $baz is array<array-key, mixed> since it can have named arguments
}Remove the offending duplicates:
<?php
$arr = [
'a' => 'one',
'b' => 'two',
'c' => 'three',
];The first matching 'c' key was removed to prevent a change in behaviour (any new duplicate keys overwrite the values of previous ones).