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Php functions

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The real power of PHP comes from its functions; it has more than 1000 built-in functions.


PHP User Defined Functions

Besides the built-in PHP functions, we can create our own functions. A function is a block of statements that can be used repeatedly in a program. A function will not execute immediately when a page loads. A function will be executed by a call to the function.


Create a User Defined Function in PHP

A user defined function declaration starts with the word "function":

Syntax

function functionName ( ) {     
    code to be executed; 
}

Note: A function name can start with a letter or underscore (not a number).
Tip: Give the function a name that reflects what the function does!

Function names are NOT case-sensitive.

In the example below, we create a function named "writeMsg()". The opening curly brace ( { ) indicates the beginning of the function code and the closing curly brace ( } ) indicates the end of the function. The function outputs "Hello world!". To call the function, just write its name:

Example

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

   writeMsg(); // call the function 
?>

PHP Function Arguments

Information can be passed to functions through arguments. An argument is just like a variable.
Arguments are specified after the function name, inside the parentheses. You can add as many arguments as you want, just separate them with a comma.

Syntax

function functionName ( $arg1, $arg2 ) {     
    code to be executed; 
}

The following example has a function with one argument ($fname). When the familyName() function is called, we also pass along a name (e.g. Jani), and the name is used inside the function, which outputs several different first names, but an equal last name:

Example

<?php 
    function familyName ($fname) { 
        echo "$fname Refsnes.<br>"; 
    } 

    familyName("Jani"); 
    familyName("Hege"); 
    familyName("Stale"); 
    familyName("Kai Jim"); 
    familyName("Borge"); 
?>

The following example has a function with two arguments ($fname and $year):

Example

<?php 
    function familyName($fname, $year) { 
       echo "$fname Refsnes. Born in $year <br>"; 
    } 

    familyName("Hege", "1975"); 
    familyName("Stale", "1978"); 
    familyName("Kai Jim", "1983"); 
?>

PHP Default Argument Value

The following example shows how to use a default parameter. If we call the function setHeight() without arguments it takes the default value as argument:

Example

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

     setHeight(350); 
     setHeight(); // will use the default value of 50 
     setHeight(135); 
     setHeight(80); 
?>

PHP Functions - Returning values

To let a function return a value, use the return statement:

Example

<?php 
    function sum($x, $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); 
?>

 

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