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English
In PHP, array_fill_keys() is a very practical function that allows us to quickly create a new array using the specified keys and set the values of all keys to the same value. So the question is: Can we use the anonymous function (Closure)** as the fill value in the array_fill_keys() function?
The answer is: Yes , but there is one thing to note.
array_fill_keys(array $keys, mixed $value): array
$keys is an array containing the key names you want to set.
$value is the value you want to assign to each key.
Although you can pass an anonymous function as $value into array_fill_keys() , it may not behave as you would expect - it does not execute this anonymous function for each key , but rather assigns the same function reference to all keys.
<?php
$keys = ['apple', 'banana', 'cherry'];
$array = array_fill_keys($keys, function() {
return rand(1, 100);
});
print_r($array);
Output result:
Array
(
[apple] => Closure Object
[banana] => Closure Object
[cherry] => Closure Object
)
As you can see, the value corresponding to each key is a Closure object, not the execution result of an anonymous function. This means that if you want each key to have a different value generated by anonymous functions, you can't do it directly.
If you want to generate a different value for each key (like a different random number), you should execute anonymous functions in the traversal:
<?php
$keys = ['apple', 'banana', 'cherry'];
$array = [];
foreach ($keys as $key) {
$array[$key] = (function() {
return rand(1, 100);
})();
}
print_r($array);
Sample output:
Array
(
[apple] => 73
[banana] => 25
[cherry] => 89
)
You can also use array_map() with key name array to achieve:
<?php
$keys = ['apple', 'banana', 'cherry'];
$array = array_combine($keys, array_map(function() {
return rand(1, 100);
}, $keys));
print_r($array);
Suppose you are developing a small application, and each module needs a default processor, you can write it like this:
<?php
$modules = ['news', 'shop', 'forum'];
$defaultHandler = function($module) {
return "https://m66.net/handler/{$module}";
};
$config = [];
foreach ($modules as $module) {
$config[$module] = $defaultHandler($module);
}
print_r($config);
Output example:
Array
(
[news] => https://m66.net/handler/news
[shop] => https://m66.net/handler/shop
[forum] => https://m66.net/handler/forum
)
array_fill_keys() supports passing in anonymous functions as values, but does not execute it.
If you want to generate dynamic values, you should call anonymous functions in loops or array_map() .
array_fill_keys() is more suitable for static value filling, while dynamic logic is recommended to be processed by traversal.
I hope this article can help you better understand the differences in usage between array_fill_keys() and anonymous functions in PHP! If you are interested in this type of underlying behavior, you might as well try to gain a deeper understanding of the behavior of PHP arrays in memory, and you may gain more.
