PHP - Lua::call() Function

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The PHP Lua::call() or __call() function is used to allow to call Lua functions. This feature helps the integration of Lua, a lightweight programming language, with PHP's functions. It allows PHP to provide data to a Lua function and then return the function's result. This is useful if you want to use Lua for specific tasks in a PHP application.

Before you can use Lua::call() in your PHP code, you have to create a Lua environment. The function can handle both simple and complex parameters. It is a helpful tool for developers that use Lua scripts in PHP projects.

Syntax

Below is the syntax of the PHP Lua::call() function −

mixed public Lua::call(callable $lua_func, array $args = ?, int $use_self = 0)
mixed public Lua::__call(callable $lua_func, array $args = ?, int $use_self = 0)

Parameters

Here are the parameters of the call() function −

• $lua_func − (Required) This Lua function is what you want to call. This method should be declared in the Lua environment before it can be used.

• $args − (Optional) It is a set of input parameters for the Lua function. These parameters will be available when the Lua function is executed. If the Lua function is empty, it is called without any parameters.

• $use_self − (Optional) It shows whether the Lua environment should be the function's context. The function uses the Lua environment as its context if the number is non-zero; if it is zero, it will not use self.

Return Value

The call() function returns the result of the Lua function execution, which can be of any type (mixed).

PHP Version

The call() function is available from version 0.9.0 of the PECL lua extension onwards.

Example 1

First we will show you the basic example of the PHP Lua::call() function that returns the sum of two numbers. The PHP code calls this Lua method and passes two numbers as arguments: 5 and 10. The final result is printed, which is the total of the two numbers, or 15.

<?php
   // Create Lua environment
   $lua = new Lua(); 
   
   // Define Lua function
   $lua->eval("function add(a, b) return a + b end"); 
   
   // Call Lua function from PHP
   $result = $lua->call('add', [5, 10]); 
   echo "Result: $result"; 
?>

Output

Here is the outcome of the following code −

Result: 15

Example 2

This code shows how to use Lua call() function inside a PHP code to calculate the total of an array. It creates a Lua environment using the Lua class. A defined Lua function called SumArray takes an array, adds up all of its elements, and then returns the total. The PHP script uses an array [1, 2, 3, 4, 5] as input to call this method. Finally, the array's total of 15 elements is printed.

<?php
   // Create Lua environment
   $lua = new Lua(); 

   $lua->eval("function sumArray(arr) local sum = 0 for _, v in ipairs(arr) do sum = sum + v end return sum end"); 
   
   // Define Lua function for summing array elements
   $result = $lua->call('sumArray', [[1, 2, 3, 4, 5]]); 
   
   echo "Result: $result";  
?> 

Output

This will generate the below output −

Result: 15

Example 3

This code shows how you can use Lua's call() function in a PHP code. A Lua environment is created and the Lua method addToSelf is defined, which adds a number to a value stored in self. Using the self context and the integer 50, the program invokes this function.

<?php
   // Create Lua environment
   $lua = new Lua(); 
   
   $lua->eval("self.value = 100; function addToSelf(num) return self.value + num end");
   
   // Define a Lua function with self-context
   $result = $lua->call('addToSelf', [50], 1); 
   
   echo "Result: $result"; 
?> 

Output

This will create the below output −

Result: 150