PHP: create an array of functions with a for loop

Question

I have some code that needs a list of functions. I want to create automatically part of this list. Scope rules in PHP prevent my following approach to the problem from working:

$list=[];
$i=0;
for(;$i<10; $i++) {
  $list []= function() { 
    // code that --depends-- on $i, like:
    return $i;
  };
}

// example of use of the 7th function in the list:
echo $list[6]();

Outputs (on my test machine I have PHP 8.1.2)

Warning: Undefined variable $i in [...]/test.php on line [...]

Because when the 7th anonymous function in $list is called by the last line, its body refers to $i, which is local to the function body and does not refer to the loop variable $i. If $i were declared global it would not issue a warning but would not do what I want either.

Notes:

In some posts here, OO programming is mentioned. But I do not know enough about OO programming and PHP to see how.
create_function is no more available in PHP 8
I know there are simpler code for outputting 6, like echo 6; thanks.

If is a simple execution, try with php.net/manual/en/functions.arrow.php — Manuel Guzman
– Manuel Guzman, Commented Jan 24, 2023 at 18:02
Thanks. From your link it appears the arrow seems to implicitly use the "use" keyword proposed in Daniel Cheung's answer. — Arnaud
– Arnaud, Commented Jan 24, 2023 at 18:58

Daniel Cheung · Accepted Answer · 2023-01-24 15:53:18Z

2

<?php
$list=[];

for($i=0;$i<10; $i++) {
  $list []= function() use ($i) { // <--
    return $i;
  };
}

echo $list[6]();

You are missing the capture phrase in PHP: https://www.php.net/manual/en/functions.anonymous.php

Closures may also inherit variables from the parent scope. Any such variables must be passed to the use language construct.

answered Jan 24, 2023 at 15:53

Daniel Cheung

4,8491 gold badge33 silver badges68 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Arnaud Over a year ago

Thanks!! This is so simple, I'm glad this keyword exists.

Collectives™ on Stack Overflow

PHP: create an array of functions with a for loop

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related