1. PHP-language, functions
Jouni Juntunen
Oulu University of Applied Sciences
School of Business and Information Management

2. Functions Two types of functions
Built-in (in PHP more that 700 prewritten functions available)
Custom
Gives well-defined structure to software
Adds reusability

3. Function syntax
Return value
Name
Parameters

4. Example: mail-function
Send from you application without any spesific knowledge about -protocols or low-level details
<?
$subject=”The subject”;
$message=”Test”;
$headers='From:' . $from . "\r\n" . 'X-Mailer: PHP/' . phpversion();
if (mail($to,$subject,$message,$headers)) .
. ?>

5. Example: printf-function
Print formatted string
Examples:
More examples on

6. Set HTTP-headers
Header-function can be used to set HTTP headers for server’s reply in PHP
Example: Relocate user (Example and source)
Example: Promt for username and password (Example and source on course material and Ilmari)

7. Input validation with functions
Check if input given by user is numerical
Validation user following PHP-functions
floatval(), intval(), strval()
Example
Source code

8. Manipulating strings For example: substr, strlen and str_replace
More string functions on

9. Example: Is credit card valid? (Luhn’s formula)
1. 4 * 2 = 8
2. 9 * 1 = 9
3. 2 * 2 = 4
4. 0 * 1 = 0
5. 1 * 2 = 2
6. 9 * 1 = 9
7. 0 * 2 = 0
8. 0 * 1 = 0
9. 7 * 2 (= 14) = 1+ 4 = 5
10. 5 * 1 = 5
11. 2 * 2 = 4
12. 6 * 1 = 6
13. 7 * 2 (=14) = = 5
14. 2 * 1 = 2
15. 7 * 2 (=14) = = 5
6 last number
= 64
(64 + 6) %10 ==0