Question 137024 in PHP Question posted in
Official manual can be found here.

Php – Enabling preg_replace_callback() replacement function if it's loaded from string

I have input strings like

Wires: 8 Pairs: 4

The both numbers may be different for different strings

So, only dividing and only numbers can be different

I need to get the output result like

Wires: 2 Pairs: 4

That is the number of wires should become the result of diving the first number by the second one

Here is my working PHP code:

<?php
$input = 'Wires: 8 Pairs: 4';
$pattern = '(Wires:)(s)(d+)(s)(Pairs:)(s)(d+)';

$output = preg_replace_callback('/'.$pattern.'/',
    function($m) {
        return 'Wires: '.$m[3]/$m[7].' Pairs: '.$m[7];
    },
$input);

echo $output;

But the point is, both patterns and replacements should be stored in and loaded from external JSON file as strings.

The patterns are working if I store them in the file, adding two escaping backslashes instead of one like (\s)(\d+)

But how to deal with the replacements?

If I try something like

<?php
$input = 'Wires: 8 Pairs: 4';
$pattern = '(Wires:)(s)(d+)(s)(Pairs:)(s)(d+)';
$replacement = 'Wires: $m[3]/$m[7] Pairs: $m[3]';

$output = preg_replace_callback('/'.$pattern.'/',
    function($m) {
        global $replacement;
        return $replacement;
    },
$input);

echo $output;

I simply get

Wires: $m[3]/$m[7] Pairs: $m[3]
Tags:

2

Answers


  1. 0

    PHP doesn’t allow you to serialize functions, so to serialize a function, you need a library such as this one: https://github.com/opis/closure

    If using a library cannot be your choice, another convenient but VERY DANGEROUS way is to use eval.

    $repl = 'return "Wires: ".$m[3]/$m[7]." Pairs: ".$m[7];';

$output = preg_replace_callback('/'.$pattern.'/',
    function($m) use ($repl) {
        return eval($repl);
    },
$input);
    Login or Signup to reply.
  2. 0

    There is absolutely no reason to store any part of this task anywhere else because you state that only the numbers will change.

    Use sprintf() to avoid quoting problems.

    Code: (Demo)

    $input = 'Wires: 8 Pairs: 4';
echo preg_replace_callback(
         '/Wires: (d+) Pairs: (d+)/',
         fn($m) => sprintf(
                 'Wires: %d Pairs: %d',
                 $m[1] / $m[2],
                 $m[2]
             ),
         $input
     );

    Or, you can use sscanf() and printf(). Demo

    sscanf($input, 'Wires: %d Pairs: %d', $wires, $pairs);
printf('Wires: %d Pairs: %d', $wires / $pairs, $pairs);
    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search