Is it possible to change inside a function from somewhere else?-CodePudding

I want to do something like this:

I have a function like this that I don't know what exactly inside it, I just know that the function should have a parameter and one return, it may have if statement, foreach or anything. I want to get function find that parameter and return, and specify it's code:

function a($param) {
     if($param > 1) {
         return $param;
      }
}

and I want to pass this function to another function and edit it and then call it:

function b(a($param)) {
     // get function code
     // change return in that function to something else like echo
     // specify if statements and anything else and change to what I want
     // and then call it and use it
}

Is this possible in php?

CodePudding user response：

Is this possible in php?

Yes, that is called code re-use. The idea is to re-use the existing function but not modifying it's code. You can have your function, too, thought.

Let's take the echo example as it's that straight forward:

echo a($param);

Done.

Now that is perhaps too trivial in your case. So why not write a function your own?:

function b($param) {
     $result = a($param);

     // ... do whatever you want with the result ...

     return $result; // finally return.
}

And then:

echo b($param); // use your function instead of the other.

This is a common way to re-use the code of functions within your own code.

If the original function is not doing what you need, take a different one that does or communicate with its author(s) to raise your issue(s).

Now what if it is not always a() but maybe a1(), a2(), ..., aN() to be used in b()?

One way to handle this is to abstract from a() by making it a function parameter of b():

function b(callable $a, $param) {
    $result = $a($param);

    // ... do whatever you want with the result ...

    return $result; // finally return.
}

Now b() can be called with any kind-of-a() function and its $param.

This might not fully suffice in your case but perhaps opens up a direction you can benefit from.

Let's see.

Perhaps the additional parameter $a stands in the way when calling b().

Previously it was:

echo a($param);

Then:

echo b($param);

And it now became:

$a = 'a' . random_int(1, 99); // $a could be any-kind-of-a()

// ...

echo b($a, $param);

Now similar to having a function as a parameter to make it "dynamic", it is also possible in PHP to have it as a return value: A function that returns a function:

function b_of_a(callable $a): callable {
    // b()'s original implementation (enclosing $a)
    return function ($param) use ($a) {
        $result = $a($param);

        // ... do whatever you want with the result ...

        return $result; // finally return.
    };
};

Similar to a() -> $a() there is now b() -> $b():

$a = 'a' . random_int(1, 99); // $a could be any-kind-of-a()

// ...

$b = b_of_a($a); // b() with any-kind-of-a() as $b 

// ...

echo $b($param);

What were fixed function names in the original code have become variables you can pass around. The way both the kind-of-a() and the kind-of-b() function calls are preserved: with the single parameter.

And while the code of b() is fixed, what is a() within it, can be injected as a parameter.