수식을 평가하는 방법 PHP에서 문자열로 전달 된?

수식을 평가하는 방법 PHP에서 문자열로 전달 된?

수학 연산을 수행하기위한 적절하고 안전한 방법을 찾기 위해 문자열을 전달했습니다. 내 시나리오에서는 이미지 EXIF ​​데이터에서 가져온 값입니다.

약간의 연구 끝에 나는 그것을하는 두 가지 방법을 발견했다.

먼저, eval을 사용합니다.

function calculator1($str){
    eval("\$str = $str;");
    return $str;
}

두 번째, create_function 사용 :

function calculator2($str){
    $fn = create_function("", "return ({$str});" );
    return $fn();
};

두 예제 모두 악의적 인 코드 실행을 피하기 위해 문자열 정리가 필요합니다. 그렇게하는 다른 방법이나 짧은 방법이 있습니까?

해결법

1. ==============================

   1.도움이 될 것입니다.

   도움이 될 것입니다.

   http://www.phpclasses.org/browse/package/2695.html

   다운로드에 성가신 로그인이 필요합니다. 나는 그것을 당신을 위해 여기에 붙여 넣었다.

       /*
       ================================================================================
   
       EvalMath - PHP Class to safely evaluate math expressions
       Copyright (C) 2005 Miles Kaufmann <http://www.twmagic.com/>
   
       ================================================================================
   
       NAME
           EvalMath - safely evaluate math expressions
   
       SYNOPSIS
           <?
             include('evalmath.class.php');
             $m = new EvalMath;
             // basic evaluation:
             $result = $m->evaluate('2+2');
             // supports: order of operation; parentheses; negation; built-in functions
             $result = $m->evaluate('-8(5/2)^2*(1-sqrt(4))-8');
             // create your own variables
             $m->evaluate('a = e^(ln(pi))');
             // or functions
             $m->evaluate('f(x,y) = x^2 + y^2 - 2x*y + 1');
             // and then use them
             $result = $m->evaluate('3*f(42,a)');
           ?>
   
       DESCRIPTION
           Use the EvalMath class when you want to evaluate mathematical expressions 
           from untrusted sources.  You can define your own variables and functions,
           which are stored in the object.  Try it, it's fun!
   
       METHODS
           $m->evalute($expr)
               Evaluates the expression and returns the result.  If an error occurs,
               prints a warning and returns false.  If $expr is a function assignment,
               returns true on success.
   
           $m->e($expr)
               A synonym for $m->evaluate().
   
           $m->vars()
               Returns an associative array of all user-defined variables and values.
   
           $m->funcs()
               Returns an array of all user-defined functions.
   
       PARAMETERS
           $m->suppress_errors
               Set to true to turn off warnings when evaluating expressions
   
           $m->last_error
               If the last evaluation failed, contains a string describing the error.
               (Useful when suppress_errors is on).
   
       AUTHOR INFORMATION
           Copyright 2005, Miles Kaufmann.
   
       LICENSE
           Redistribution and use in source and binary forms, with or without
           modification, are permitted provided that the following conditions are
           met:
   
           1   Redistributions of source code must retain the above copyright
               notice, this list of conditions and the following disclaimer.
           2.  Redistributions in binary form must reproduce the above copyright
               notice, this list of conditions and the following disclaimer in the
               documentation and/or other materials provided with the distribution.
           3.  The name of the author may not be used to endorse or promote
               products derived from this software without specific prior written
               permission.
   
           THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
           IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
           WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
           DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
           INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
           (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
           SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
           HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
           STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
           ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
           POSSIBILITY OF SUCH DAMAGE.
   
       */
   
       class EvalMath {
   
           var $suppress_errors = false;
           var $last_error = null;
   
           var $v = array('e'=>2.71,'pi'=>3.14); // variables (and constants)
           var $f = array(); // user-defined functions
           var $vb = array('e', 'pi'); // constants
           var $fb = array(  // built-in functions
               'sin','sinh','arcsin','asin','arcsinh','asinh',
               'cos','cosh','arccos','acos','arccosh','acosh',
               'tan','tanh','arctan','atan','arctanh','atanh',
               'sqrt','abs','ln','log');
   
           function EvalMath() {
               // make the variables a little more accurate
               $this->v['pi'] = pi();
               $this->v['e'] = exp(1);
           }
   
           function e($expr) {
               return $this->evaluate($expr);
           }
   
           function evaluate($expr) {
               $this->last_error = null;
               $expr = trim($expr);
               if (substr($expr, -1, 1) == ';') $expr = substr($expr, 0, strlen($expr)-1); // strip semicolons at the end
               //===============
               // is it a variable assignment?
               if (preg_match('/^\s*([a-z]\w*)\s*=\s*(.+)$/', $expr, $matches)) {
                   if (in_array($matches[1], $this->vb)) { // make sure we're not assigning to a constant
                       return $this->trigger("cannot assign to constant '$matches[1]'");
                   }
                   if (($tmp = $this->pfx($this->nfx($matches[2]))) === false) return false; // get the result and make sure it's good
                   $this->v[$matches[1]] = $tmp; // if so, stick it in the variable array
                   return $this->v[$matches[1]]; // and return the resulting value
               //===============
               // is it a function assignment?
               } elseif (preg_match('/^\s*([a-z]\w*)\s*\(\s*([a-z]\w*(?:\s*,\s*[a-z]\w*)*)\s*\)\s*=\s*(.+)$/', $expr, $matches)) {
                   $fnn = $matches[1]; // get the function name
                   if (in_array($matches[1], $this->fb)) { // make sure it isn't built in
                       return $this->trigger("cannot redefine built-in function '$matches[1]()'");
                   }
                   $args = explode(",", preg_replace("/\s+/", "", $matches[2])); // get the arguments
                   if (($stack = $this->nfx($matches[3])) === false) return false; // see if it can be converted to postfix
                   for ($i = 0; $i<count($stack); $i++) { // freeze the state of the non-argument variables
                       $token = $stack[$i];
                       if (preg_match('/^[a-z]\w*$/', $token) and !in_array($token, $args)) {
                           if (array_key_exists($token, $this->v)) {
                               $stack[$i] = $this->v[$token];
                           } else {
                               return $this->trigger("undefined variable '$token' in function definition");
                           }
                       }
                   }
                   $this->f[$fnn] = array('args'=>$args, 'func'=>$stack);
                   return true;
               //===============
               } else {
                   return $this->pfx($this->nfx($expr)); // straight up evaluation, woo
               }
           }
   
           function vars() {
               $output = $this->v;
               unset($output['pi']);
               unset($output['e']);
               return $output;
           }
   
           function funcs() {
               $output = array();
               foreach ($this->f as $fnn=>$dat)
                   $output[] = $fnn . '(' . implode(',', $dat['args']) . ')';
               return $output;
           }
   
           //===================== HERE BE INTERNAL METHODS ====================\\
   
           // Convert infix to postfix notation
           function nfx($expr) {
   
               $index = 0;
               $stack = new EvalMathStack;
               $output = array(); // postfix form of expression, to be passed to pfx()
               $expr = trim(strtolower($expr));
   
               $ops   = array('+', '-', '*', '/', '^', '_');
               $ops_r = array('+'=>0,'-'=>0,'*'=>0,'/'=>0,'^'=>1); // right-associative operator?  
               $ops_p = array('+'=>0,'-'=>0,'*'=>1,'/'=>1,'_'=>1,'^'=>2); // operator precedence
   
               $expecting_op = false; // we use this in syntax-checking the expression
                                      // and determining when a - is a negation
   
               if (preg_match("/[^\w\s+*^\/()\.,-]/", $expr, $matches)) { // make sure the characters are all good
                   return $this->trigger("illegal character '{$matches[0]}'");
               }
   
               while(1) { // 1 Infinite Loop ;)
                   $op = substr($expr, $index, 1); // get the first character at the current index
                   // find out if we're currently at the beginning of a number/variable/function/parenthesis/operand
                   $ex = preg_match('/^([a-z]\w*\(?|\d+(?:\.\d*)?|\.\d+|\()/', substr($expr, $index), $match);
                   //===============
                   if ($op == '-' and !$expecting_op) { // is it a negation instead of a minus?
                       $stack->push('_'); // put a negation on the stack
                       $index++;
                   } elseif ($op == '_') { // we have to explicitly deny this, because it's legal on the stack 
                       return $this->trigger("illegal character '_'"); // but not in the input expression
                   //===============
                   } elseif ((in_array($op, $ops) or $ex) and $expecting_op) { // are we putting an operator on the stack?
                       if ($ex) { // are we expecting an operator but have a number/variable/function/opening parethesis?
                           $op = '*'; $index--; // it's an implicit multiplication
                       }
                       // heart of the algorithm:
                       while($stack->count > 0 and ($o2 = $stack->last()) and in_array($o2, $ops) and ($ops_r[$op] ? $ops_p[$op] < $ops_p[$o2] : $ops_p[$op] <= $ops_p[$o2])) {
                           $output[] = $stack->pop(); // pop stuff off the stack into the output
                       }
                       // many thanks: http://en.wikipedia.org/wiki/Reverse_Polish_notation#The_algorithm_in_detail
                       $stack->push($op); // finally put OUR operator onto the stack
                       $index++;
                       $expecting_op = false;
                   //===============
                   } elseif ($op == ')' and $expecting_op) { // ready to close a parenthesis?
                       while (($o2 = $stack->pop()) != '(') { // pop off the stack back to the last (
                           if (is_null($o2)) return $this->trigger("unexpected ')'");
                           else $output[] = $o2;
                       }
                       if (preg_match("/^([a-z]\w*)\($/", $stack->last(2), $matches)) { // did we just close a function?
                           $fnn = $matches[1]; // get the function name
                           $arg_count = $stack->pop(); // see how many arguments there were (cleverly stored on the stack, thank you)
                           $output[] = $stack->pop(); // pop the function and push onto the output
                           if (in_array($fnn, $this->fb)) { // check the argument count
                               if($arg_count > 1)
                                   return $this->trigger("too many arguments ($arg_count given, 1 expected)");
                           } elseif (array_key_exists($fnn, $this->f)) {
                               if ($arg_count != count($this->f[$fnn]['args']))
                                   return $this->trigger("wrong number of arguments ($arg_count given, " . count($this->f[$fnn]['args']) . " expected)");
                           } else { // did we somehow push a non-function on the stack? this should never happen
                               return $this->trigger("internal error");
                           }
                       }
                       $index++;
                   //===============
                   } elseif ($op == ',' and $expecting_op) { // did we just finish a function argument?
                       while (($o2 = $stack->pop()) != '(') { 
                           if (is_null($o2)) return $this->trigger("unexpected ','"); // oops, never had a (
                           else $output[] = $o2; // pop the argument expression stuff and push onto the output
                       }
                       // make sure there was a function
                       if (!preg_match("/^([a-z]\w*)\($/", $stack->last(2), $matches))
                           return $this->trigger("unexpected ','");
                       $stack->push($stack->pop()+1); // increment the argument count
                       $stack->push('('); // put the ( back on, we'll need to pop back to it again
                       $index++;
                       $expecting_op = false;
                   //===============
                   } elseif ($op == '(' and !$expecting_op) {
                       $stack->push('('); // that was easy
                       $index++;
                       $allow_neg = true;
                   //===============
                   } elseif ($ex and !$expecting_op) { // do we now have a function/variable/number?
                       $expecting_op = true;
                       $val = $match[1];
                       if (preg_match("/^([a-z]\w*)\($/", $val, $matches)) { // may be func, or variable w/ implicit multiplication against parentheses...
                           if (in_array($matches[1], $this->fb) or array_key_exists($matches[1], $this->f)) { // it's a func
                               $stack->push($val);
                               $stack->push(1);
                               $stack->push('(');
                               $expecting_op = false;
                           } else { // it's a var w/ implicit multiplication
                               $val = $matches[1];
                               $output[] = $val;
                           }
                       } else { // it's a plain old var or num
                           $output[] = $val;
                       }
                       $index += strlen($val);
                   //===============
                   } elseif ($op == ')') { // miscellaneous error checking
                       return $this->trigger("unexpected ')'");
                   } elseif (in_array($op, $ops) and !$expecting_op) {
                       return $this->trigger("unexpected operator '$op'");
                   } else { // I don't even want to know what you did to get here
                       return $this->trigger("an unexpected error occured");
                   }
                   if ($index == strlen($expr)) {
                       if (in_array($op, $ops)) { // did we end with an operator? bad.
                           return $this->trigger("operator '$op' lacks operand");
                       } else {
                           break;
                       }
                   }
                   while (substr($expr, $index, 1) == ' ') { // step the index past whitespace (pretty much turns whitespace 
                       $index++;                             // into implicit multiplication if no operator is there)
                   }
   
               } 
               while (!is_null($op = $stack->pop())) { // pop everything off the stack and push onto output
                   if ($op == '(') return $this->trigger("expecting ')'"); // if there are (s on the stack, ()s were unbalanced
                   $output[] = $op;
               }
               return $output;
           }
   
           // evaluate postfix notation
           function pfx($tokens, $vars = array()) {
   
               if ($tokens == false) return false;
   
               $stack = new EvalMathStack;
   
               foreach ($tokens as $token) { // nice and easy
                   // if the token is a binary operator, pop two values off the stack, do the operation, and push the result back on
                   if (in_array($token, array('+', '-', '*', '/', '^'))) {
                       if (is_null($op2 = $stack->pop())) return $this->trigger("internal error");
                       if (is_null($op1 = $stack->pop())) return $this->trigger("internal error");
                       switch ($token) {
                           case '+':
                               $stack->push($op1+$op2); break;
                           case '-':
                               $stack->push($op1-$op2); break;
                           case '*':
                               $stack->push($op1*$op2); break;
                           case '/':
                               if ($op2 == 0) return $this->trigger("division by zero");
                               $stack->push($op1/$op2); break;
                           case '^':
                               $stack->push(pow($op1, $op2)); break;
                       }
                   // if the token is a unary operator, pop one value off the stack, do the operation, and push it back on
                   } elseif ($token == "_") {
                       $stack->push(-1*$stack->pop());
                   // if the token is a function, pop arguments off the stack, hand them to the function, and push the result back on
                   } elseif (preg_match("/^([a-z]\w*)\($/", $token, $matches)) { // it's a function!
                       $fnn = $matches[1];
                       if (in_array($fnn, $this->fb)) { // built-in function:
                           if (is_null($op1 = $stack->pop())) return $this->trigger("internal error");
                           $fnn = preg_replace("/^arc/", "a", $fnn); // for the 'arc' trig synonyms
                           if ($fnn == 'ln') $fnn = 'log';
                           eval('$stack->push(' . $fnn . '($op1));'); // perfectly safe eval()
                       } elseif (array_key_exists($fnn, $this->f)) { // user function
                           // get args
                           $args = array();
                           for ($i = count($this->f[$fnn]['args'])-1; $i >= 0; $i--) {
                               if (is_null($args[$this->f[$fnn]['args'][$i]] = $stack->pop())) return $this->trigger("internal error");
                           }
                           $stack->push($this->pfx($this->f[$fnn]['func'], $args)); // yay... recursion!!!!
                       }
                   // if the token is a number or variable, push it on the stack
                   } else {
                       if (is_numeric($token)) {
                           $stack->push($token);
                       } elseif (array_key_exists($token, $this->v)) {
                           $stack->push($this->v[$token]);
                       } elseif (array_key_exists($token, $vars)) {
                           $stack->push($vars[$token]);
                       } else {
                           return $this->trigger("undefined variable '$token'");
                       }
                   }
               }
               // when we're out of tokens, the stack should have a single element, the final result
               if ($stack->count != 1) return $this->trigger("internal error");
               return $stack->pop();
           }
   
           // trigger an error, but nicely, if need be
           function trigger($msg) {
               $this->last_error = $msg;
               if (!$this->suppress_errors) trigger_error($msg, E_USER_WARNING);
               return false;
           }
       }
   
       // for internal use
       class EvalMathStack {
   
           var $stack = array();
           var $count = 0;
   
           function push($val) {
               $this->stack[$this->count] = $val;
               $this->count++;
           }
   
           function pop() {
               if ($this->count > 0) {
                   $this->count--;
                   return $this->stack[$this->count];
               }
               return null;
           }
   
           function last($n=1) {
               return $this->stack[$this->count-$n];
           }
       }
   

   편집 : 지터는 역 폴란드어 표기법을 지원하는 버전을 원했습니다. 내가 HP 계산기를 가졌을 때 대학 시절을 생각 나게한다. :)

       <?php
       /* This Class can be useful for writting RPN macros or FORTH like parsers 
              @Author: Arturo Gonzalez-Mata Santana (Spain)
                    arturogmata@gmail.com
           @copyright 2007: www.phpsqlasp.com
   
           It is part of a project to recover "macros" from some old aplications 
   
       This code is free software; you can redistribute it and/or
       modify it under the terms of the GNU General Public License
       as published by the Free Software Foundation; either version 3
       of the License, or (at your option) any later version.
   
       This program is distributed in the hope that it will be useful,
       but WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
       GNU General Public License for more details.
   
       You should have received a copy of the GNU General Public License
       along with this program; if not, write to the Free Software
       Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
       */
       class RPNstack
       {
           var $data=array();
           var $compare=0;
           function pop() {return array_shift ($this->data);}
           function push($x) {array_unshift($this->data, $x);}
           function count() {return count($this->data);}
           function first() {return $this->data[0];}
           function top() {return end($this->data);}  //last element of 
           function swap() { // interchange tow elements
               $t = $this->data[1];
               $this->data[1] = $this->data[0];
               $this->data[0] = $t;
               }
           function dup() {  // put a copy of X element in the stack
               array_unshift($this->data, $this->data[0]);
               }
   
           function dump(){ // dump array data for debuging
               print_r($this->data);
               }
   
           function parse($tok)  // execute actions with the stack for each token
           {
               $r = null;
               $tok = strtoupper(trim($tok));
               //$this->dump(); // this line is for debugging purpose only
               switch ($tok) :
                   // FIRST "IF THEN" AND OTHER FLOW CONTROLS
                   case ('THEN'): break;
                   case('IF'):
                       if ($this->pop() == 0) do {  // if condition is false do nothing until "THEN"
                           $tok = strtoupper(strtok (" "));
                           } while ($tok <> "THEN");  // IF THERE IS NO "THEN" THIS SHALL BE AN ENLESS LOOP
                       break;
   
                   //   basic math operators   //OPERADORES MATEMATICOS BASICOS
                   case('+'):
                       $r = $this->pop() + $this->pop();
                       // $r = array_shift($this->data) + array_shift($this->data);  // is more efficient but less understable
                       break;        
                   case('-'):
                       $r = $this->pop(); $r = $this->pop()-$r;
                       break;
                   case('*'):
                       $r = $this->pop() *  $this->pop();
                       break;
                   case('/'):
                       $r = $this->pop(); $r = $this->pop() / $r;
                       break;
                   // stack operators  //OPERADORES DE PILA  
                   case ('DUP'):
                       $r=$this->dup();
                       break;
                   case ('SWAP'):
                       $this->swap();
                       break;
   
                   // COMPARISON OPERATORS
                   case ('='):
                       if ($this->data[0] == $this->data[1]) $r = $this->push(1);
                       else $r = $this->push(0);
                       break;
                   case ('<>'):
                       if ($this->data[0] <> $this->data[1]) $r = $this->push(1);
                       else $r = $this->push(0);
                       break;
                   case ('<'):
                       if ($this->data[0] < $this->data[1]) $r = $this->push(1);  
                       else $r = $this->push(0);                            
                       break;
                   case ('>'):
                       if ($this->data[0] > $this->data[1])  $r = $this->push(1);  
                       else $r = $this->push(0);                            
                       break;
                   case ('>='):
                       if ($this->data[0] >= $this->data[1])  $r = $this->push(1);  
                       else $r = $this->push(0);                            
                       break;
                   case ('<='):
                       if ($this->data[0] <= $this->data[1])  $r = $this->push(1);  
                       else $r = $this->push(0);                            
                       break;
   
                   // WARNING FOR NON IMPLEMENTED FUNCTIONS
                   default:
                           return sprintf('I don\'t know how to "%s" ', $tok);
               endswitch;
               if (!is_null($r)) $this->push($r); 
               return $r;
           } // parse
   
   
           function parse_line($cadena)
           {
               $tok = strtok ($cadena," ");
               while ($tok!= '') {
                   if (is_numeric ($tok)) {
                       $this->push($tok);
                   } else {
                       $r = $this->parse($tok);
                   }
                   $tok = strtok (" ");
               }
               return $r;
           }
   
       } // class RPN
   
   
   
       ?>
   

from https://stackoverflow.com/questions/1015242/how-to-evaluate-formula-passed-as-string-in-php by cc-by-sa and MIT license