How can I create and execute a series of PHP Variable Functions in a for loop?

Question

I'm unfamilar with using variable functions in PHP, but I've repeatedly re-read the manual:

https://www.php.net/manual/en/functions.variable-functions.php

and it's not at all clear what I'm doing wrong here:

for ($i = 0; $i < 10000; $i++) {

  $Function_Name = 'Test_Function_'.sprintf('%03d', $i);

  function $Function_Name() {

    echo  __FUNCTION__.' is working.';
  }

  $Function_Name();
}

Why is this loop not creating and running 10000 variable functions?

Alternative using anonymous functions

An alternative approach (using anonymous functions) doesn't seem to work either:

for ($i = 0; $i < 10000; $i++) {

  $Function_Name = 'Test_Function_'.sprintf('%03d', $i);

  ${$Function_Name} = function () {

    echo  __FUNCTION__.' is working.';
  }

  ${$Function_Name}();
}

What are you trying to achieve here? I see no possible way this could actually be useful. — Niet the Dark Absol
– Niet the Dark Absol, Commented Jun 6, 2020 at 11:39
I am setting up a speed test. Creating and running 10,000 functions will give me the baseline. Then I will compare against creating and including 10,000 files containing functions. Then I will compare against creating and eval()-ing 10,000 strings. — Rounin
– Rounin, Commented Jun 6, 2020 at 11:41
you cannot define a function with a variable. You must use the name of the variable function Function_Name() { — user1986815
– user1986815, Commented Jun 6, 2020 at 11:42
You could just use anonymous functions. $some_function = function() { /* do stuff */ } and then call $some_function(); — Niet the Dark Absol
– Niet the Dark Absol, Commented Jun 6, 2020 at 11:42
Thanks, @NiettheDarkAbsol. Before I posted I did attempt an alternative approach using anonymous functions (now added to the question above) but I couldn't make that work, either. — Rounin
– Rounin, Commented Jun 6, 2020 at 11:49

Stefanov.sm · Accepted Answer · 2020-06-06 12:08:07Z

1

Please note that anonymous (lambda) functions only see (closure) variables from the external scope if they are explicitly listed with "use" i.e.

${$Function_Name} = function () use ($Function_Name)

and then it works as expected.

for ($i = 0; $i < 10000; $i++) 
{    
  $Function_Name = 'Test_Function_'.sprintf('%03d', $i);
  ${$Function_Name} = function () use ($Function_Name)
  {
    echo  $Function_Name.' is working.'.PHP_EOL;
  };
  ${$Function_Name}();
}

edited Jun 6, 2020 at 12:08

answered Jun 6, 2020 at 12:01

Stefanov.sm

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2 Comments

Rounin Over a year ago

Brilliant work, Stefanov.sm. @NiettheDarkAbsol was also right that I should use an anonymous function, which I'd tried, but what I'd missed in my own test (and still visible in my question at the top) is that I had failed to demarcate the end of the assignment with a ;. Your tip regarding use is very helpful. Thank you.

Rounin Over a year ago

More on deploying use in this context here: blog.dubbelboer.com/2012/04/07/php-use-keyword.html

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