README

A stand-alone php library for parsing and running formulas

Installation via composer

composer require asylum29/php-formula-interpreter

How does it work ?

First, create an instance of \Mormat\FormulaInterpreter\Compiler

$compiler = new \Mormat\FormulaInterpreter\Compiler();

Then use the compile()method to parse the formula you want to interpret. It will return an instance of \Mormat\FormulaInterpreter\Executable :

$executable = $compiler->compile('2 + 2');

Finally run the formula from the executable :

$result = $executable->run();
// $result equals 4

Examples of formulas

// variables can be used
price + 2 

// parenthesis can be used
(1 + 2) * 3 

// default functions are available
sqrt(4) 

// complex formulas can be used
(((100 * 0.43075) * 1.1 * 1.5) / (1-0.425)) * 1.105 

// string are supported
lowercase('FOO')

// arrays are supported
count([2, 3, 4])

// custom functions can be registered
your_function_here(2) 

// use the in operator to check if an item is in array
1 in [1, 2, 3]  // returns true

// use the in operator to check if a substring is in a string
'Wars' in 'Star Wars'

Supported types in formulas

Numeric values

A numeric value can be an integer or a float

    2       // integer
    2.30    // float

String values

Use simple quote to delimiter strings

    'foobar'

Array values

Use comma to separate items and brackets to wrap the items

    [1, 2, 3]

Functions, strings and operations can be used as an item of an array

    [cos(0), 'foobar', 2 + 2]

Using operators

The following operators are available :

The operators *, \ are being evaluated first, then the operators + and -

You can also force the prioriry of an expression by using parentheses like this

2 * (3 + 2)

You can use as many parentheses as you like.

2 * (2 * (3 + 2 * (3 + 2)) + 2)

Using variables

A variable is just a word inside your formula like this :

price * rate / 100

Just before executing a formula in PHP, make sure to inject all the required variables in an array

$variables = array(
   'price' => 40.2,
   'rate' => 12.8
);

$executable->run($variables);

Using functions

Availables functions

How to register a custom function ?

Use the registerCustomFunction() method in the \Mormat\FormulaInterpreter\Compiler class.

The custom function must implement the \Mormat\FormulaInterpreter\Functions\FunctionInterface. This interface contains the methods below :

getName() returns the name of the function
supports($arguments) returns true if the $arguments send to the function are valid.
execute($arguments) executes the function and returns the value.

Why this library ?

Some user could wants to perform a simple calculation and being able to change it as much as he can. Before using a library, you could use the eval function. But this method has two major drawbacks :

Security. A php script is being evaluated by the eval function. Php is a very powerful language, perhaps too powerful for a user especially when the user wants to inject malicious code.
Complexity. Php is also complex for someone who doesn't understand programming language. It could be nice to interpret an excel-like formula instead.

asylum29 / php-formula-interpreter

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