Chapter 3 Introduction to PHP

1. Chapter 3 Introduction to PHP

2. By default, PHP documents end with the extension .php • files ending with .htmor .html to also get parsed by the PHP processor • To trigger the PHP commands, you need to learn a new tag. The first part is: <?phpthe closing part is encountered, which looks like this: ?> Incorporating PHP Within HTML

3. A small PHP “Hello World” program might look like <?php echo "Hello world"; ?> • all the examples from this book have been archived onto a specially created companion website at http://lpmj.net Calling the PHP Parser

4. There are two ways in which you can add comments • // This is a comment • after a line of code $x += 10; // Increment $x by 10 • When you need multiple-line comments <?php /* This is a section of multiline comments which will not be interpreted */ ?> Using Comments

5. Semicolons $x += 10; You must place a $ in front of all variables <?php $mycounter = 1; $mystring = "Hello"; $myarray = array("One", "Two", "Three"); ?> Basic Syntax

6. String variables $username = "Fred Smith"; <?php // test1.php $username = "Fred Smith"; echo $username; echo "<br />"; $current_user = $username; echo $current_user; ?> Understanding Variables

7. $count = 17; to store the number 17 in the variable $count • $count = 17.5; a floating-point number (containing a decimal point); • Arrays $team = array('Bill', 'Joe', 'Mike', 'Chris', 'Jim'); • Two-dimensional arrays <?php $oxo = array(array('x', '', 'o'), array('o', 'o', 'x'), array('x', 'o', '' )); ?> Numeric variables

8. four rules: • • Variable names must start with a letter of the alphabet or the _ (underscore) character. • • Variable names can contain only the characters: a-z, A-Z, 0-9, and _ (underscore). • • Variable names may not contain spaces. If a variable must comprise more than one word it should be separated with the _ (underscore) character. (e.g., $user_name). • • Variable names are case-sensitive. The variable $High_Score is not the same as the variable $high_score. Variable naming rules

9. Operators are the mathematical, string, comparison, and logical commands such as plus, minus, times, and divide. PHP looks a lot like plain arithmetic; for instance, the following statement outputs 8: echo 6 + 2; Operators

10. Arithmetic operators

11. Assignment operators

12. Comparison operators

13. Logical operators

14. The syntax to assign a value to a variable is always variable = value. Or, to reassign the value to another variable, it is other variable = variable. • Variable incrementing and decrementing • String concatenation uses the period (.) to append one string of characters to another. The simplest way to do this is as follows: echo "You have " . $msgs . " messages."; Variable Assignment

15. Example 3-6. A multiline string echo statement <?php $author = "Alfred E Newman"; echo "This is a Headline This is the first line. This is the second. Written by $author."; ?> Multiple-Line Commands

16. Variables do not have to be declared before they are used, and that PHP always converts variables to the type required by their context when they are accessed. Variable Typing

17. Constants are similar to variables, holding information to be accessed later, except that they are what they sound like—constant Constants

18. echo cannot be used as part of a more complex expression, whereas print can $b ? print "TRUE" : print "FALSE"; • The question mark is simply a way of interrogating whether variable $b is true or false. Whichever command is on the left of the following colon is executed if $b is true, whereas the command to the right is executed if $b is false Echo and print Commands

19. A simple function declaration <?php function longdate($timestamp) { return date("l F jS Y", $timestamp); } ?> Functions

20. To declare a variable as having global scope, use the keyword global Global variables

21. <?php function test() { static $count = 0; echo $count; $count++; } ?> A function using a static variable

22. PHP’ssuperglobal variables