The real power of PHP comes from its functions.

In PHP, there are more than 700 built-in functions.

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PHP Built-in Functions

For a complete reference and examples of the built-in functions, please visit our PHP Reference.

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PHP Functions

In this chapter we will show you how to create your own functions.

To keep the browser from executing a script when the page loads, you can put your script into a function.

A function will be executed by a call to the function.

You may call a function from anywhere within a page.

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Create a PHP Function

A function will be executed by a call to the function.

Syntax

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function functionName() { code to be executed; } ____________________________________________________________________

PHP function guidelines:

• Give the function a name that reflects what the function does
• The function name can start with a letter or underscore (not a number)

Example

A simple function that writes my name when it is called:

____________________________________________________________________ function writeName() { echo "Kai Jim Refsnes"; } echo "My name is "; writeName(); ?> ____________________________________________________________________

Output:

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My name is Kai Jim Refsnes

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PHP Functions - Adding parameters

To add more functionality to a function, we can add parameters. A parameter is just like a variable.

Parameters are specified after the function name, inside the parentheses.

Example 1

The following example will write different first names, but equal last name:

____________________________________________________________________ function writeName($fname) { echo $fname . " Refsnes. "; } echo "My name is "; writeName("Kai Jim"); echo "My sister's name is "; writeName("Hege"); echo "My brother's name is "; writeName("Stale"); ?> ____________________________________________________________________

Output:

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My name is Kai Jim Refsnes. My sister's name is Hege Refsnes. My brother's name is Stale Refsnes. ____________________________________________________________________

Example 2

The following function has two parameters:

____________________________________________________________________ function writeName($fname,$punctuation) { echo $fname . " Refsnes" . $punctuation . " "; } echo "My name is "; writeName("Kai Jim","."); echo "My sister's name is "; writeName("Hege","!"); echo "My brother's name is "; writeName("Ståle","?"); ?> ____________________________________________________________________

Output:

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My name is Kai Jim Refsnes. My sister's name is Hege Refsnes! My brother's name is Ståle Refsnes? ____________________________________________________________________

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PHP Functions - Return values

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

Example

____________________________________________________________________ function add($x,$y) { $total=$x+$y; return $total; } echo "1 + 16 = " . add(1,16); ?> ____________________________________________________________________

Output:

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1 + 16 = 17 ____________________________________________________________________