Pass an expression that I want to evaluate as parameter to PHP function-CodePudding

I have a PHP function that is supposed return corresponding list of values for given input. Here is its code:

function output_values($s, $e, $d, $exp = '$i*$i') {
  for($i = $s; $i <= $e; $i = $d) {
    echo eval($exp);
    // Put the value of $i in $exp and get the result.
  }
}

The expression will always be mathematical like $i*$i or 3*$i 8 etc.

I got the following error with it:

syntax error, unexpected end of file in eval()'d code

I know that I can use array_map(). However, that function still requires me to pass the expression myself. In this case, I won't know the expression whose value I need to evaluate beforehand.

I hope I am making it clear.

Thanks.

CodePudding user response：

To pass an expression, or any code in general, use functions:

function output_values($s, $e, $d, callable $exp) {
  for ($i = $s; $i <= $e; $i  = $d) {
    echo $exp($i);
  }
}

output_values(1, 6, 2, fn ($i) => $i * $i);