How to Efficiently Pass Variables into Laravel's `whereExists` Subqueries?

Passing Variables into Laravel's Advanced Wheres

In Laravel, using subqueries with the whereExists method can be straightforward. However, challenges arise when external variables need to be incorporated within the closure. The use of external variables, such as $this->city->id, can make the code less efficient.

Solution: Utilizing the 'use' Keyword

To address this issue, the use keyword allows the necessary variables to be passed into the closure from the parent scope. This approach enables the convenient use of external variables within the closure.

For instance:

DB::table('users')
    ->where(function ($query) use ($activated) {
        $query->where('activated', '=', $activated);
    })
    ->get();

PHP 7.4 Update: Arrow Functions

PHP 7.4 introduces arrow functions, a more concise form of anonymous functions. This provides an even more simplified way to pass variables into closures.

Here's an example using arrow functions in PHP 7.4:

DB::table('users')
    ->where(fn($query) => $query->where('activated', '=', $activated))
    ->get();

Compared to the regular syntax, arrow functions have the following differences:

• They use the fn keyword instead of function.
• They capture all variables from the parent scope automatically, eliminating the need for the use keyword.
• They always return a value, making void return type declarations impossible.
• They must omit the return keyword.
• They must be defined as a single expression, limiting multi-line functions but allowing method chaining.

The above is the detailed content of How to Efficiently Pass Variables into Laravel's `whereExists` Subqueries?. For more information, please follow other related articles on the PHP Chinese website!