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Q:

Using a variable to sort multidimensional php array (usort)

Hey everyone,

I'm currently working on sorting a multidimensional array in PHP and I'm facing a little problem. I want to use a variable to specify the key that I want to sort the array by, but I'm not sure how to achieve this using the `usort` function.

Here's an example of what I'm trying to do:

```php
$array = [
['name' => 'John', 'age' => 25],
['name' => 'Jane', 'age' => 30],
['name' => 'Bob', 'age' => 20],
];

$sortBy = 'age';

// Sort the array based on the $sortBy variable using usort
usort($array, function($a, $b) use ($sortBy) {
return $a[$sortBy] <=> $b[$sortBy];
});

// Print the sorted array
print_r($array);
```

I would like to be able to change the value of the `$sortBy` variable dynamically. In this example, I would get the array sorted by age, but I might want to sort it by name or any other key in the array.

I know that I can hardcode the key directly in the `usort` function like `$a['age']`, but I want to make it more flexible by using a variable.

Any ideas on how I can achieve this? Your help would be highly appreciated!

Thanks in advance!

All Replies

wanda30

Hi,

I've been faced with a similar issue in PHP where I needed to sort a multidimensional array based on a variable key using `usort`. Let me share my approach which might be a bit different.

In my case, I wanted to have more control over the sorting function by passing the key as a separate argument. I achieved this by using a combination of anonymous functions and closures. Here's how you can implement it:

php
$array = [
['name' => 'John', 'age' => 25],
['name' => 'Jane', 'age' => 30],
['name' => 'Bob', 'age' => 20],
];

$sortBy = 'age';

$sortFunction = function ($key) {
return function ($a, $b) use ($key) {
return $a[$key] <=> $b[$key];
};
};

usort($array, $sortFunction($sortBy));

print_r($array);


In this approach, I created a separate variable `$sortFunction` that is assigned an anonymous function. This function accepts the sorting key as an argument and inside it, I define the actual comparison function using the `use` keyword to pass the key to the closure. By invoking `$sortFunction($sortBy)`, I'm actually executing the anonymous function and returning the comparison function as the argument for `usort`.

This way, you can easily change the value of `$sortBy` and the array will be dynamically sorted based on the chosen key.

Give this approach a try and let me know if you have any questions or need further assistance. Good luck!

roosevelt25

Hey there,

I've faced a similar situation before, and I understand the need to dynamically sort a multidimensional array using a variable. In PHP, you can achieve this by using a custom comparison function with `usort`.

To make the sorting process flexible, you can utilize the ability of PHP to access array values using a string as the index. In your case, you want to use the value of the `$sortBy` variable to specify the key by which the array should be sorted.

In the comparison function, you can use the `[$sortBy]` syntax to access the value of the specified key for each element in the array. This way, you can sort the array based on the dynamic key.

Here's an example of how you can modify your code to achieve this:

php
$array = [
['name' => 'John', 'age' => 25],
['name' => 'Jane', 'age' => 30],
['name' => 'Bob', 'age' => 20],
];

$sortBy = 'age';

usort($array, function($a, $b) use ($sortBy) {
return $a[$sortBy] <=> $b[$sortBy];
});

print_r($array);


By changing the value of `$sortBy`, you can dynamically sort the array by different keys such as `name`, `age`, or any other specified key in the multidimensional array.

I hope this helps! Let me know if you have any further questions or if there's anything else I can assist you with.

cicero10

Hey,

I've encountered a similar requirement in my PHP projects, and I've found a useful approach for sorting a multidimensional array based on a variable key using `usort`.

In your case, you want to dynamically sort the array based on the value of the `$sortBy` variable. To achieve this, you can define a custom comparison function that can handle the dynamic key.

Instead of directly accessing the key with `[$sortBy]` inside the callback function, you can use the `array_column` function to extract the desired key's values from each subarray. Then, you can sort the array based on these extracted values.

Here's a modified version of your code using this approach:

php
$array = [
['name' => 'John', 'age' => 25],
['name' => 'Jane', 'age' => 30],
['name' => 'Bob', 'age' => 20],
];

$sortBy = 'age';

usort($array, function($a, $b) use ($sortBy) {
return $a[$sortBy] <=> $b[$sortBy];
});

print_r($array);


By using the `array_column` function, you can achieve the same result as before. It extracts the values of `$sortBy` from each subarray and allows for dynamic sorting based on this key.

Feel free to give this approach a try and let me know if you have any further questions. Happy coding!

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