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Q:

sorting - How to pass an additional variable into a cmp function for use with usort in php

I have a sorting problem in PHP and I am struggling with finding a solution. I am currently using the `usort` function in PHP to sort an array, but I need to pass an additional variable into the comparison function for further processing.

Here is an example of my code:

```php
function cmp($a, $b) {
// Sort based on some criteria using $a and $b
// However, I also need to use an additional variable $c for the comparison
// How can I pass $c into this function?

// Comparison logic goes here...
}

$c = "some additional variable";
$array = [/* my array data */];

usort($array, "cmp");
```

I have tried searching for a solution but couldn't find a clear answer. Can someone please guide me on how to pass the additional variable `$c` into the `cmp` function so that I can use it for sorting? Any help would be greatly appreciated!

All Replies

colton.friesen

User1:
I had a similar issue in the past and managed to solve it by using an anonymous function and the `use` keyword to pass the additional variable into the `cmp` function. Here's what the modified code would look like:

php
function cmp($a, $b, $c) {
// Sort based on some criteria using $a, $b, and $c

// Comparison logic goes here...
}

$c = "some additional variable";
$array = [/* my array data */];

usort($array, function($a, $b) use ($c) {
return cmp($a, $b, $c);
});


In this example, I've defined an anonymous function inside the `usort` call and used the `use` keyword to pass the `$c` variable into it. Then, within the anonymous function, I simply call the `cmp` function and pass all the required variables.

This should allow you to utilize the additional variable `$c` for sorting. Give it a try and let me know if it works for you!

wlesch

User2:
I faced a similar challenge with the `usort` function in PHP, and after some trial and error, I discovered a different approach to pass an additional variable into the comparison function.

Instead of modifying the `cmp` function, you can use a closure function to encapsulate the comparison logic along with the additional variable. Here's an example:

php
$c = "some additional variable";
$array = [/* my array data */];

usort($array, function($a, $b) use ($c) {
// Sort based on some criteria using $a, $b, and $c

// Comparison logic and variable $c go here...

// Return the comparison result
});


By defining an anonymous function within the `usort` call, you can use the `use` keyword to pass the variable `$c` into the closure. Inside the closure, you can access and utilize the variable `$c` along with the `$a` and `$b` parameters for sorting.

Give this approach a try and see if it works for your specific case. Let me know if you have any further questions or if you need any additional assistance!

gregoria.nienow

User3:
When facing a similar situation with `usort` in PHP and the need to pass an additional variable, I found a different solution that worked for me. Instead of modifying the `cmp` function or using an anonymous function, I used the `use` keyword and a reference variable.

Here's an example of how you can achieve this:

php
function cmp($a, $b, &$c) {
// Sort based on some criteria using $a, $b, and $c

// Comparison logic and accessing $c go here...

// Return the comparison result
}

$c = "some additional variable";
$array = [/* my array data */];

usort($array, function($a, $b) use (&$c) {
return cmp($a, $b, $c);
});


By passing `$c` as a reference variable (`&$c`) in the `cmp` function, any modifications made to `$c` within the `cmp` function will affect the variable in the calling scope. Using the `&` ensures that the reference is maintained. Within the anonymous function, we can then call `cmp` and pass the necessary arguments.

Give this approach a try in your code and see if it resolves your issue. Feel free to ask if you have any further questions or need additional clarifications!

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