1. Review 3
csc242 – web programming

2. PHP – General Syntax Double vs. single quotes
$var= “hi”;
echo “$var “ . “John!”;
-> hi John!
echo ‘$var ‘ . “John!”;
-> $var John!
$_POST[‘foo’]= “bar”;
print “$_POST[‘bar’]”;
-> syntax error!!!
print “{$_POST[‘bar’]}”;
-> bar
Double vs. single quotes
Variables inside double quotes will be evaluated
Variables inside single quotes will not be evaluated
Dot (.) is the string concatenation operator
Must enclose array variables in braces {} for the to print properly!

3. PHP - arrays Standard arrays Associative arrays (arbitrary indicies)
Useful functions
count($arr)
Number of elements
is_array($arr)
Is it an array?
isset($arr[“third”])
Is the value set?
unset($arr[“third”])
Remove a value
Standard arrays
$list = array(‘john’, ‘mary’, ‘fred’);
Automatically indexed starting at zero ($list[0] is “john”)
Associative arrays (arbitrary indicies)
$arr= array(“first” => “one”, “second” => “two”);
arr[“third”]= “three”;
Looping
for($i=0; $i< count($arr); $i++) { … }
foreach ($arr as $key => $value) { … }
sets $key and $value on each iteration
foreach ($arr as $value) { … }
just does the values

4. PHP - Functions Declare with function keyword
No need to specify return type!
Arguments passed by value
Variables can be made global with the global keyword
Default arguments are allowed
return statement
Can return arrays…
function addn($x, $n = 3) {
global $z;
$y= $x + $n;
$z = 2*$y;
return $y; }

5. Cookies
Allows information to be stored and accessed across pages on a web site.
To create: setcookie(‘name’,’value’);
To access: $var= $_COOKIE[‘name’];
To remove: setcookie(‘name’);
Storage is on the client side
MUST be set up in PHP before any HTML is sent to the client
Can be blocked by the client (disabled in the browser)

6. Sessions Rely on cookies to operate Advantages over cookies
One cookie is created for the session ID
Therefore MUST be set up in PHP before any HTML is sent to the client
Advantages over cookies
Can be made to work without cookies
ini_set("session.use_trans_sid", 1);
uses “get” to pass session ID between web pages
Can store more information than cookies

7. Sessions (cont.) To begin: session_start(); To end: session_destroy();
Session ID: session_id(); (or $_COOKIE['PHPSESSID']})
Store information using $_SESSION array:
$_SESSION[‘foo’] = ‘bar’;
It can be accessed on any page that has started a session

8. Relational databases (MySQL)
Information is stored in tables
Table column lists the type of information stored
Table rows contain the actual data entries
Tables are often “linked” (an ID in one table is referenced in another)
Like the Products and Categories tables in the grocery store project
SQL commands allow access to table information
SELECT column1, … columnN FROM table_name WHERE columnX = ‘value’
INSERT into table_name (col1, col2, …) VALUES (‘val1’, ‘val2’, …)
- Many others…

9. More info in the Basic SQL commands Powerpoint
mysqli functions
$connection= mysqli_connect(host, user, password, database)
mysqli_close($connection);
$error= mysqli_error($connection);
$result= mysqli_query($connection, SQLcommand);
$number= mysqli_num_rows($result);
$value= get_mysqli_result($result, $number, $field);
This is a command provided for CSC242 that replaces the mysql_result() command
More info in the Basic SQL commands Powerpoint