How to Create and call a Function

Function syntax

function function_name([$param_1, $param_2, ... , $param_n]) {
  // Code for function
  [return [value];] // optional
}

How to define a function

A function with no parameters that returns a value

      function coin_toss() {

        $coin = (random_int(0, 1) == 0) ? 'heads' : 'tails'; // ternary conditional

        return $coin;

      } 
      Coin is: heads

A function with one parameter

      
      $error = "This is an error!";

      function display_error($error) { 

        echo("<p class='error'>$error</p>\n"); 

      }

Calling a Function

display_error($error);OutputThis is an error!

A function with three parameters that returns a value

      $x = 10;

      $y = 20;

      $z = 30;

      function avg_of_3($x, $y, $z) { 

        $avg = ($x + $y + $z) / 3; 

        return $avg; 

      }

      avg_of_3($x, $y, $z);

      echo("<p>Average of $x + $y + $z is " . avg_of_3($x, $y, $z) . "</p>\n");
      Average of 10 + 20 + 30 is 20

How to call a function

Functions that return values

      
      $average = avg_of_3(5, 2, 8); // average is 5

      echo coin_toss(); // display heads or tails
      
      Output
      tails

A function that doesn’t return a value

      
      display_error('Value out of range.');

Discarding the return value

      
       $list = array('Apples', 'Oranges', 'Grapes'); 

       $last = array_pop($list); // Removes Grapes – stores return value

       array_pop($list); // Removes Oranges – discards return value

A function is a reusable block of code. To code a function, code the function keyword followed by the name of the function, followed by a set of parentheses.
Within the parentheses of a function, you can code an optional parameter list that contains one or more parameters.
To code a function that returns data, code a return statement in the body of the function. The return statement ends the execution of the function and returns the specified value. If you don’t specify a value in the return statement, it returns NULL.
To code a function that doesn’t return data, don’t include a return statement.
When you call a function, the arguments in the argument list must be in the same order as the parameters in the parameter list defined by the function, and they must have compatible data types.

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