Create a function

                
                    <?php
                    function writeMsg() {
                      echo "Hello world!";
                    }
                    
                    writeMsg();
                    ?>
                
                

Function with one argument

                
                    <?php
                    function familyName($fname) {
                      echo "$fname Refsnes.<br>";
                    }
                    
                    familyName("Jani");
                    familyName("Hege");
                    familyName("Stale");
                    familyName("Kai Jim");
                    familyName("Borge");
                    ?>
                
                

Function with two arguments

                
                    <?php
                    function familyName($fname, $year) {
                      echo "$fname Refsnes. Born in $year <br>";
                    }
                    
                    familyName("Hege","1975");
                    familyName("Stale","1978");
                    familyName("Kai Jim","1983");
                    ?>
                
                

Function with default argument value

                
                    <?php
                    function setHeight(int $minheight = 50) {
                      echo "The height is : $minheight <br>";
                    }
                    
                    setHeight(350);
                    setHeight();
                    setHeight(135);
                    setHeight(80);
                    ?>
                
                

Function that returns a value

                
                    <?php
                    function sum(int $x, int $y) {
                      $z = $x + $y;
                      return $z;
                    }
                    
                    echo "5 + 10 = " . sum(5,10) . "<br>";
                    echo "7 + 13 = " . sum(7,13) . "<br>";
                    echo "2 + 4 = " . sum(2,4);
                    ?>
                
                

Return type declarations

                
                    <?php declare(strict_types=1); // strict requirement
                    function addNumbers(float $a, float $b) : float {
                      return $a + $b;
                    }
                    echo addNumbers(1.2, 5.2); 
                    ?>
                    
                
                

Passing arguments by reference

                
                    <?php
                    function add_five(&$value) {
                      $value += 5;
                    }
                    
                    $num = 2;
                    add_five($num);
                    echo $num;
                    ?>