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array_fill_keys is a very useful array function in PHP to fill an array based on the specified key value. If you encounter situations where the results and expectations returned when using this function are inconsistent, don't worry. I will use a specific example and explanation to help you find the root cause of the problem.
First, let's take a look at the basic syntax of the array_fill_keys function:
array_fill_keys(array $keys, mixed $value): array
$keys : an array that needs to be an array key.
$value : The value corresponding to each key.
This function returns a new array whose keys come from the $keys parameter, and all values are filled with $value .
Let's look at a common usage:
<?php
$keys = ['a', 'b', 'c'];
$value = 10;
$result = array_fill_keys($keys, $value);
print_r($result);
?>
The output will be:
Array
(
[a] => 10
[b] => 10
[c] => 10
)
Assuming you use similar code, but the result returned is different from what you expect, there may be several reasons. Let's look at situations that may lead to inconsistencies.
If the $keys array contains duplicate elements, array_fill_keys will set the corresponding value of the key based on the last duplicate key. for example:
<?php
$keys = ['a', 'b', 'a'];
$value = 10;
$result = array_fill_keys($keys, $value);
print_r($result);
?>
The output will be:
Array
(
[a] => 10
[b] => 10
)
In the above code, 'a' is repeatedly defined twice, but array_fill_keys only retains one 'a' key and its value is 10 . This does not raise an error, but due to the uniqueness of the array keys, duplicate keys will be deduplicated.
If the $keys array you pass to array_fill_keys is empty, then the returned array will be an empty array:
<?php
$keys = [];
$value = 10;
$result = array_fill_keys($keys, $value);
print_r($result);
?>
Output:
Array
(
)
In this case, the function does not cause any problems, but the result does not have the expected content.
array_fill_keys When array_fill_keys uses keys to the array, the type of key name will affect the result. For example, if the key is a numeric type, array_fill_keys treats it as an integer key. Consider the following example:
<?php
$keys = [1, 2, 3];
$value = 'hello';
$result = array_fill_keys($keys, $value);
print_r($result);
?>
Output:
Array
(
[1] => hello
[2] => hello
[3] => hello
)
If the key is of string type, it will cause the index of the array to change.
Check if the key array has duplicate values : Make sure that the $keys array has no duplicate elements. You can use array_unique() to deduplicate it, or directly check the array.
Confirm the type of the array key : If you want the key to be a string type, you can make sure that the elements of the $keys array are all string types, or cast key types.
Debugging and output : Use var_dump() instead of print_r() so that you can see the key type and details, which helps identify potential problems.
array_fill_keys is a very useful function, but you need to pay attention to the key type and array structure to avoid inconsistent results caused by duplicate keys or type mismatch. If you find that the output does not meet expectations, you can troubleshoot the problem from the above aspects.
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