PHP 5 Functions
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PHP 5 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
?>Run example »
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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.
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 "$fname Refsnes.<br>";
familyName("Jani");
familyName("Hege");
familyName("Stale");
familyName("Kai Jim");
familyName("Borge");
?>Run example »
The following example has a function with two arguments ($fname and $year):
Example
<?php
function familyName($fname, $year)
echo "$fname Refsnes. Born in $year <br>";
familyName("Hege", "1975");
familyName("Stale", "1978");
familyName("Kai Jim", "1983");
?>Run example »
PHP Default Argument Value
The following example shows how to use a default parameter. If we call the
function setHeight() without arguments it takes the default value as argument:
Example
<?php
function setHeight($minheight = 50)
echo "The height is : $minheight <br>";
setHeight(350);
setHeight(); // will use the default value of 50
setHeight(135);
setHeight(80);
?>Run example »
PHP Functions - Returning values
To let a function return a value, use the return statement:
Example
<?php
function sum($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);
?>Run example »
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