如何安全高效地处理用户输入的数学表达式？mossadal/math-parser助你构建智能应用

<code class="bash">composer require mossadal/math-parser</code>

<code class="php"><?php

require 'vendor/autoload.php';

use MathParser\StdMathParser;
use MathParser\Interpreting\Evaluator;

$parser = new StdMathParser();
$evaluator = new Evaluator();

// 解析表达式 "1+2"
$AST = $parser->parse('1+2');

// 对AST进行求值
$value = $AST->accept($evaluator);
echo "1+2 = " . $value; // 输出: 1+2 = 3

?></code>

<code class="php"><?php

require 'vendor/autoload.php';

use MathParser\StdMathParser;
use MathParser\Interpreting\Evaluator;

$parser = new StdMathParser();
$evaluator = new Evaluator();

// 解析表达式 "x + sqrt(y)"
$AST = $parser->parse('x + sqrt(y)');

// 设置变量x和y的值
$evaluator->setVariables([
    'x' => 2,
    'y' => 9
]);

// 求值
$value = $AST->accept($evaluator);
echo "x + sqrt(y) (x=2, y=9) = " . $value; // 输出: x + sqrt(y) (x=2, y=9) = 5

?></code>

<code class="php"><?php

require 'vendor/autoload.php';

use MathParser\StdMathParser;
use MathParser\Interpreting\Differentiator;
use MathParser\Interpreting\Evaluator;
use MathParser\Interpreting\LaTeXGenerator; // 用于美观展示导数表达式

$parser = new StdMathParser();
$evaluator = new Evaluator();
$latexGenerator = new LaTeXGenerator();

// 定义原始表达式：exp(2*x) - x*y
$f = $parser->parse('exp(2*x) - x*y');

// 创建求导器，指定对变量 'x' 求导
$differentiator = new Differentiator('x');
$df = $f->accept($differentiator); // $df 现在是导数表达式的AST

echo "原始表达式 (f): " . $f->accept($latexGenerator) . "\n";
echo "对x的导数 (df/dx): " . $df->accept($latexGenerator) . "\n"; // 输出类似: e^{2x} \cdot 2 - y

// 求导数在特定点的值
$evaluator->setVariables([
    'x' => 1,
    'y' => 2
]);
$df_value = $df->accept($evaluator);
echo "当 x=1, y=2 时，导数的值为: " . $df_value . "\n"; // 预期输出: 2 * e^2 - 2 ≈ 12.778

?></code>