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# 如何计算PHP中作为字符串传递的公式？

2019-07-10 16:51:33

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

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

## 2 回答

http：/www.phpclasses.org/浏览/包/2695.html

/*

================================================================================

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');

\$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

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];

}

}

<?php

/* This Class can be useful for writting RPN macros or FORTH like parsers

@Author: Arturo Gonzalez-Mata Santana (Spain)

arturogmata@gmail.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

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

{

while (\$tok!= '') {

if (is_numeric (\$tok)) {

\$this->push(\$tok);

} else {

\$r = \$this->parse(\$tok);

}

\$tok = strtok (" ");

}

return \$r;

}

} // class RPN

?>

Qyouu

# 它是怎么工作的？

`\$formulaInterpreter = new FormulaInterpreter("x + y", ["x" => 10, "y" => 20]);`

`echo \$formulaInterpreter->execute();`

`echo (new FormulaInterpreter("x + y", ["x" => 10, "y" => 20]))->execute();`

# 实例

```# Formula: speed = distance / time\$speed = (new FormulaInterpreter("distance/time", ["distance" => 338, "time" => 5]))->e
xecute() ;echo \$speed;#Venezuela night overtime (ordinary_work_day in hours): (normal_salary * days_in_a_work_month)/ordinary_work
_day\$parameters = ["normal_salary" => 21000, "days_in_a_work_month" => 30, "ordinary_work_day" => 8];\$venezuelaLOTTTArt118NightOvertime = (
new FormulaInterpreter("(normal_salary/days_in_a_work_month)/ordinary_work_day", \$parameters))->execute();echo \$venezuelaLOTTTArt118Nig

# 关于公式

1. 它必须至少包含两个操作数和一个运算符。
2. 操作数的名称可以是大写的，也可以是小写的。
3. 到目前为止，数学函数是sin，cos，pow…。不包括在内。我正在努力把它们包括进去。
4. 如果公式无效，则会收到如下错误消息：

错误，您的公式(单变量)无效。

5. 参数的值必须是数值。

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