Php function as function's parameter

Question

In my php project I have some functions that in some cases I want to call under try-catch block, and in some cases not under try-catch block. And now I want to write a function that gets some function as parameter, calls it and return false in case of exception.

Approximately code like this and with support of different numbers of parameters for 'someFunction'.

function tryTo($someFunctionName) {
    try {
        return someFunctionName();
    } catch (Exception $error) {
        return false;
    }

How to organize that?

except for the missing dollar sign, what is the problem with this code? — trincot
– trincot, Commented Aug 18, 2016 at 8:04
Of course, you might also need to consider passing arguments to the function that you're calling — Mark Baker
– Mark Baker, Commented Aug 18, 2016 at 8:15
Yes, I want to call function inside try-catch block with parameters. — Vahag Chakhoyan
– Vahag Chakhoyan, Commented Aug 18, 2016 at 8:17

trincot · Accepted Answer · 2016-08-18 08:16:02Z

You need to define your original functions as Closures so they are represented by variables and can be passed as function arguments.

Here is example code:

function myFunc ($arg) {
    echo "called myFunc with '$arg' as argument";
}

// create a Closure for it
$myFunc = function ($arg) { myFunc($arg); };

function tryTo($someFunctionName, $arg) {
    try {
        return $someFunctionName($arg);
    } catch (Exception $error) {
        return false;
    }
}

// call tryTo passing the Closure and the argument
echo tryTo($myFunc, "test");

As of PHP 5.6 you can also use the spread operator which makes it a piece of cake to support multiple arguments. That way one tryIt function can host for functions with different numbers of parameters:

function tryTo($someFunctionName, ...$args) {
    try {
        return $someFunctionName(...$args);
    } catch (Exception $error) {
        return false;
    }
}

Tanveer Hussain · Accepted Answer · 2016-08-18 08:06:06Z

0

<?php 
function tryTo($someFunctionName) {
  try {
    return $someFunctionName();
} catch (Exception $error) {
    return false;
}

// call tryTo function by passing function name
tryTo(functionName);
?>

answered Aug 18, 2016 at 8:06

Tanveer Hussain

1237 bronze badges

3 Comments

RiggsFolly Over a year ago

Why should the OP "use this code"? A good answer will always have an explanation of what was done and why it was done that way, not only for the OP but for future visitors to SO that may find this question and be reading your answer.

Vahag Chakhoyan Over a year ago

And what will I do if I want to call 'someFunction' with parameters?

Daniel W. Over a year ago

Please do not post code-only answers. Always add an explanation.

YamiTenshi · Accepted Answer · 2016-08-18 08:50:29Z

PHP allows you to call a number of things as if they were functions - this includes:

function names as strings (for instance "myFunc")
arrays containing a function name as the first element and an array of arguments as the second element (for instance ["myFunc", ["arg1", "arg2"]])
arrays containing an object as the first element and an array of arguments as the second element (for instance [new MyClass(), ["arg1", "arg2"]])
instances of classes implementing the __invoke() magic method
Closures/anonymous functions

All of these can be denoted by the callable typehint. As such, implementing your function as such:

tryTo(callable $callable) {
    try {
        $callable();
    catch(\Exception $ex) {
        return false;
    }
}

would allow you to use tryTo() for anything PHP considers callable, and enforce that whatever you pass can be used to call a function.

So the following will work:

tryTo('myFunc'); // Equivalent to myFunc();
tryTo('MyClass::myFunc'); // Equivalent to MyClass::myFunc();
tryTo(['myFunc', ['myArg', 'myOtherArg']]; // Equivalent to myFunc('myArg', 'myOtherArg');
tryTo([new MyClass(), 'myFunc']); // Equivalent to (new MyClass())->myFunc();
tryTo(function() { echo 'test'; }); // executes whatever closure you pass

You can see here for more information.

That said, I'm seriously questioning the use case for a function like that - generally, exceptions shouldn't happen unless something is wrong, and using a function like that opens you up to silent failures. At the very least, you should log the exception that occurred so you can see that something went wrong, but in my opinion you should handle specific exceptions wherever they're relevant. That, however, is an entirely different discussion altogether and does nothing to answer your question.

In my case I am throwing Exceptions myself, to handle them after.

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