Pass extra parameters to usort callback

How to Pass Extra Parameters to usort Callback in PHP?

Are you struggling to pass extra parameters to the usort callback function in PHP? Don't worry, you're not alone! Many developers find it confusing at first, especially when they need to reuse the same code with different parameters. In this blog post, we'll explore how you can overcome this challenge and make your code more flexible.

Understanding the Problem

First, let's understand the problem before diving into the solution. The code snippet you provided is trying to sort an array of objects ($terms) based on the artist_lastname property using the usort function. However, you want to make the code reusable by passing different metadata properties to the sorting function.

The Solution

To pass extra parameters to the usort callback function, you can use an anonymous function or a callable object. However, the anonymous function approach might not work for you since you mentioned that your PHP version is 5.2.17 which doesn't support anonymous functions.

In this case, we can create a workaround using the following steps:

Step 1: Modify the sort_by_term_meta function to accept an additional parameter, $meta_value.

function sort_by_term_meta($terms, $meta, $meta_value) {
  usort($terms, create_sort_callback($meta, $meta_value));
}

Step 2: Create a new function, create_sort_callback, which returns a callable function that includes the desired $meta_value.

function create_sort_callback($meta, $meta_value) {
  return function($a, $b) use ($meta, $meta_value) {
    $name_a = get_term_meta($a->term_id, $meta_value, true);
    $name_b = get_term_meta($b->term_id, $meta_value, true);
    return strcmp($name_a, $name_b);
  };
}

Step 3: Finally, call the modified sort_by_term_meta function by passing the additional parameter.

sort_by_term_meta($terms, 'artist_lastname', 'some_meta_property');

Now, whenever you want to sort the $terms array by a specific metadata property, you can simply call the sort_by_term_meta function and pass the desired $meta_value.

💡 Pro Tips:

• You can also modify the create_sort_callback function to accept multiple metadata properties and dynamically apply them in the sorting process.

• To ensure backward compatibility, check your PHP version using PHP_VERSION constant and fallback to the original code if anonymous functions are not available.

Conclusion

Passing extra parameters to the usort callback function can be a bit tricky, especially in older PHP versions. However, by using a workaround like the one described above, you can easily achieve the desired flexibility in your code.

Now that you have the solution, go ahead and give it a try! Feel free to share your experience or ask any questions in the comments below. Happy coding!