preg_replace_callback_array Doesn't return match calculation value

Question

I try preg_replace_callback_array for math bbcode. Its returning as plain text while i require calculated result

<?php
$kode = array (
  "/\[math\]([0-9+\-\/*\)\(]+?)\[\/math\]/" =>
    function($matches) {$value = "$matches[1]"; return $value;},
);
$body = 'my result is [math]100-3[/math]';

echo preg_replace_callback_array($kode,$body);
?>

Bbcode work fine but doesn’t return calculation

If i use [math]100+10[/math] it return 100+10 but i want to get 110 here

You need to write code that parses and executes the mathematical expression. Just using the variable doesn't execute it. — Barmar, Mar 21 '19 at 07:53
If you do that, someone could write `[math]unlink("some_important_file");[/math]` — Barmar, Mar 21 '19 at 07:55
Dupe of [How to make a calculator in PHP?](https://stackoverflow.com/questions/12692727/how-to-make-a-calculator-in-php). — salathe, Mar 21 '19 at 07:56
it was work fine on this but /e modifier not support in php7 $kode = array ( "/\[math\]([0-9+\-\/*\)\(]+?)\[\/math\]/e"=>'$1', ); $body = 'my result is [math]100-3[/math]'; echo preg_replace(array_keys($kode),array_values($kode),$body); — OH Pavel, Mar 21 '19 at 07:57

score 1 · Answer 1 · answered Mar 21 '19 at 07:57

1

This is, in general, difficult. Your evaluation $value = "$matches[1]" would simply evaluate the string value. There is no simple function in PHP core library to convert a numerical calculation formula string into the result.

You may, however, learn to install chriskonnertz/string-calc with Composer and use it.

<?php

use ChrisKonnertz\StringCalc\StringCalc;

$kode = array (
  "/\[math\]([0-9+\-\/*\)\(]+?)\[\/math\]/" => function($matches) {
    $calc = new StringCalc();
    return $calc->calculate($matches[1]);
  },
);
$body = 'my result is [math]100-3[/math]';

echo preg_replace_callback_array($kode,$body);
?>

answered Mar 21 '19 at 07:57

Koala Yeung

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It was work without composar on 5.6 but on php 7 /e modifier not working $kode = array ( "/\[math\]([0-9+\-\/*\)\(]+?)\[\/math\]/e"=>'$1', ); $body = 'my result is [math]100-3[/math]'; echo preg_replace(array_keys($kode),array_values($kode),$body); – OH Pavel Mar 21 '19 at 08:03
Nice, I wasn't aware of that. +1. – Toto Mar 21 '19 at 10:08
The [PCRE modifier `e`](https://php.net/manual/en/reference.pcre.pattern.modifiers.php#reference.pcre.pattern.modifiers) was DEPRECATED in PHP 5.5.0, and REMOVED as of PHP 7.0.0. You simply cannot use it anymore in PHP 7+. – Koala Yeung Mar 22 '19 at 02:43
But that would be a neat trick for older versions of PHP. Didn't know about it. Thanks :-) – Koala Yeung Mar 22 '19 at 02:46

score 0 · Answer 2 · answered Mar 21 '19 at 08:25

You can do it with eval(). This is normally a very dangerous function, but your pattern only matches simple numerical expressions, so it's safe here.

$kode = array (
  '/\[math\]([0-9+\-\/*)(]+?)\[\/math\]/' =>
    function($matches) {eval("\$value = $matches[1];"); return $value;},
);

score 0 · Answer 3 · answered Mar 21 '19 at 09:18

thanks everyone for reply i make it working like this

  $kode = array (
  "/\[math\]([0-9+\-\/*\)\(]+?)\[\/math\]/" =>
    function($matches) {$value = "$matches[1]"; return eval('return ' . $value . ';');},
);
$body = 'my result is [math]100-3[/math]';

echo preg_replace_callback_array($kode,$body);

preg_replace_callback_array Doesn't return match calculation value

3 Answers3