Can I pass a PHP function some code to execute via a function argument?

Question

Newbie question...

Is it possible to use a function's argument to pass code to be executed inside the function? Something like...

function myfunction($somecode)
{
    $somecode;
}

myfunction("echo 'foo'");

Actual scenario: my function performs some image manipulation using Imagick...

function myfunction($imagePath)
{
    $image = new Imagick($imagePath);
    $image->gaussianBlurImage(0, 5);
}
myfunction("test.jpg");

I'd like to be able to specify the Imagick method to use on the image in a function argument, so I could have something like...

function myfunction($imagePath, $method)
{
    $image = new Imagick($imagePath);
    $image->$method;
}
myfunction("test.jpg", "thumbnailImage(100, 100)");

Is such a thing possible?

Either use eval or pass a closure which accepts $image as argument. — mario
– mario, Commented Sep 17, 2015 at 3:38
@mario what about Variable functions php.net/manual/en/functions.variable-functions.php — Funk Forty Niner
– Funk Forty Niner, Commented Sep 17, 2015 at 3:43
@Fred-ii- Sure, would also fit. If it's just a single extra function call, then splitting args into e.g. myfunc($img, "thumbnail", 100, 100) would even look tidier. — mario
– mario, Commented Sep 17, 2015 at 3:48
Variable functions are good here. Also, perhaps consider being more strict about the $methods that you will accept, and run through a switch(). That way, you can handle exceptions / unknown methods. — Charlie Schliesser
– Charlie Schliesser, Commented Sep 17, 2015 at 3:54
The method proposed by @CharlieS I feel this is probably the best way, you can insure that you have the proper number/type of arguments, provide defaults, and failing everything else issue meaningful exceptions. — Orangepill
– Orangepill, Commented Sep 17, 2015 at 4:06

Orangepill · Accepted Answer · 2015-09-17 04:55:36Z

1

Instead of using anonymous functions and variable variables you could also do this with call_user_func_array

function myfunction($imagePath, $method, array $arguments)
{
    $image = new Imagick($imagePath);
    call_user_func_array([$image, $method], $arguments);
}
myfunction("test.jpg", "thumbnailImage", [100,100]);

For additional safety you can check the methods against a whitelist of available methods for the Imagick object.

edited Sep 17, 2015 at 4:55

answered Sep 17, 2015 at 4:01

Orangepill

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3 Comments

Toutouwai Over a year ago

Thanks Orangepill, got this to work with a couple of changes to syntax: function myfunction($imagePath, $method, array $arguments) { $image = new Imagick($imagePath); call_user_func_array(array($image, $method), $arguments); } myfunction("test.jpg", "thumbnailImage", array(100, 100));

Orangepill Over a year ago

If the changes are changing the short array syntax, [] to array() then you are using an unsupported version of php and should update as soon as possible.

Toutouwai Over a year ago

Sorry, the short array syntax is fine. It's just my code editor that's out of date - it was highlighting the [,] syntax as an error.

Anthony Rutledge · Accepted Answer · 2015-09-17 04:05:48Z

0

Programming PHP (Lerdorf, Tatroe, & MacIntyre), 2nd Edition. Ch. 3, p. 73

Anonymous Functions

"You can create an anonymous function using create_function()."

PHP Manual: create_function()

$lamda = create_function( '$param1,param2', 'code;' );

But, there is more to know in PHP 5.3 and later. From example #2 of the PHP Manual under Anonymous Functions.

$greet = function($name)
{
    printf("Hello %s\r\n", $name);
};

PHP Manual: Anonymous Functions

edited Sep 17, 2015 at 4:05

answered Sep 17, 2015 at 3:52

Anthony Rutledge

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8 Comments

Marty Over a year ago

If you are using PHP 5.3.0 or newer a native anonymous function should be used instead.

Funk Forty Niner Over a year ago

yeah, that one I did think about mentioning to the OP ^

Anthony Rutledge Over a year ago

@Marty I assumed one would discover this by clicking on the link.

Marty Over a year ago

Of course, however that information seems important enough that if the link broke for whatever reason or someone passing by was too lazy to click it, a comment still follows to mention it.

Anthony Rutledge Over a year ago

@Marty Good thing Google has a going concern.

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