LIS651 lecture 1 PHP basics , database introduction

Thomas Krichel 2005-10-29 LIS651 lecture 1PHP basics, database introduction

today • PHP part • we work with • text • numbers • Booleans and flow control • arrays • we reorganize the shop • Database theory • Introduction to mySQL.

strings • a piece of text in PHP is called a string. • A string is often surrounded by single quotes. print 'I want beer'; $want='beer'; print 'I want $want'; // prints: I want $want • If you want to use the values of variables, use double quotes $want='beer'; print "I want $want"; // prints: I want beer

single and double quotes • You can use single quotes to quote double quotes print 'She wrote: "I want beer." and sighed.'; // prints: She wrote: "I want beer." and sighed. • and vice versa print "She wrote: 'I want beer.' and sighed"; // prints: She wrote: 'I want beer.' and sighed. • Sometimes it is not obvious when to put single quotes, double quotes, and when to leave them out. If one thing does not work, try something else.

the backslash escape • The backslash is used to quote characters in a that otherwise are special. print 'Don\'t give me bad beer!'; $kind='bock'; $beer='Festbock' print "<p class=\"$kind\">$beer</p>"; // prints: <p class="bock">Festbock</p> • The backslash itself is quoted as \\ print "a \\ against beer consumption"; // prints: a \ against beer consumption

more backslash escapes • \n makes the newline character • \r make the carriage return (no use in Unix) • \t makes the tab (seldomly used in HTML) • \$ makes the dollar (used in the shop) • $amount='1.50'; • print "you owe \$$amount per bottle."; • // prints: you owe $1.50 per bottle. If the backslash was not there $ would be considered to be a variable.

string functions • There are a long list of string functions in the PHP reference manual. When you work with text, you should look at those string functions at http://www.php.net/manual/en/ref.strings.php • Working with text is particularly important when checking the input of users into your form. • I am looking at just a few of examples here. You really need to read the reference to see what is available.

trim() • trim(string) removes the whitespace at the beginning and the end of the string string. It returns the transformed string. $input " Festbock "; $output=trim($input); print "|$output|"; // prints: |Festbock| • whitespace is any of the following characters • the blank character • the newline • the carriage return • the tabulation character

strlen() • strlen(string) returns the length of the string string. $zip=trim($_POST['zipcode']); $zip_length=strlen($zip); print $zip_length; // hopefully, prints 5

strip_tags() • strip_tagS(string) removes HTML tags from the string string $input="<b>But</b>weiser"; print strip_tags($input); // prints: Butweiser $in="<a href=\"http://porn.com\"><img src=\"http://porn.com/ad.gif\"/></a>"; print strip_tags($in); // prints nothing, hurray!

htmlentities() • htmlentities(string) makes HTML entities out of HTML special chars in the string string. <,>,&, and " are transformed. It returns the transformed string. $in="What does the <div> element do?"; print htmlentities($in); // prints: What does the <div> element do?

addslashes() • if a variable read from a form, say, for example a user name Antoine d'Amstel, contains a single or double quote, this can be very problematic in certain later treatments. Use addslashes(string) to add slashes to user input that may contain quotation characters. • stripslashes(string) does the opposite.

numbers • Numbers are set without the use of quotes. • You can +, -, * and / for the the basic calculations. • There also is the modulus operator %. It gives the reminder of the division of the first number by the second print 10 % 7; // prints 3 • Use parenthesis for complicated calculations $pack=2 * (10 % 7); print "a $pack pack"; // prints: a 6 pack

other number functions • abs() calculates the absolute value print abs(-3) // prints: 3 print abs(3) // prints: 3 • The list of functions that use numbers is http://www.php.net/manual/en/ref.math.php

geeky increment/decrement • ++ is an operator that adds one. The value of the resulting expression depends on the position of the operator $a=4; print ++$a; // prints: 5 print $a; // prints: 5 $b=4; print $b++; // prints 4 print $b; // prints 5 • -- works in the same way

variable names • Variable name must start with a letter or underscore. They can contain letters, digits and underscores. The following are examples of illegal names • $2drunk • $bottle-content • $brewer@grosswald • Variable names are case sensitive. I use lowercase only and add underscores in long names. • It is good to give variables meaningful names.

concatenation • This is done with the . operator. $cost=5.23; $message='This costs ' . $cost; print $message; // prints: This costs 5.23 • PHP sees that 5.23 is a number but will treat it as a string for this purpose.

geeky combined operators • There are some combined operators that change a value and set it to the new one. For example $a+=$b ; • is the same as $a=$a+$b; • Same effect for -=, *=, /=, %=, and .= $a="I want "; $b="Balitka 8"; $a.=$b; echo $a; // prints: "I want Baltika 8"

Boolean value • Every expression in PHP has a Boolean value. • It is either 'true' or 'false'. • In certain situation, an expression is evaluated as a Boolean • For example if(expression) expression1 or expression2

what is truth? • All strings are true except • the empty string • the string "0" • All numbers are true except • 0 • 0.0 • example $a=5-4-1; // $a is false • Note that variables that you have not assigned contents are false. This includes misspelled variables!!

comparison operators • Expressions that are evaluated in Boolean often use comparison operators. $beer == 'grosswald' // checks for equality • note difference from $beer='grosswald'; // this is always true • Other comparisons are < smaller than <= smaller or equal than > larger than >= larger or equal than

logical operators • 'and' is logical AND. 'or' is logical OR. if($brand=='Budweiser' or $brand="Sam Adams") { echo "Commiserations for buying a lousy beer\n"; } # where is the mistake in this piece of code? • 'not' is Boolean NOT • These can be combined. Use parenthesis if((($pints) > 2 and ($vehicle=='car')) or (($pints > 6) and ($vehicle=='bicycle'))) { print "order a cab!\n"; }

variable types • Variables in PHP have types. You can check for types is_numeric() is_string() is_int() is_float() • They all return a Boolean value. • They can be used to check the nature of a variable.

if() { } • if(expression) evaluates an expression expression as Boolean, and executes a block of code surrounded by curly brackets if the expression is true. if($drunk) { print "Dont\'t drive!\n"; } • Note you don't need to indent the block as done above, but the way Thomas has done it there is pretty much standard, so do it in the same way.

if() {} else {} • if you have an if() you can add an else block of code to execute when the condition is false if($sober) { print "You can drive\n"; } else { print "Check if you are fit to drive\n"; }

elseif() { } • You can build chain of conditions if($pints_drunk==0) { print "You are ok to drive\n"; } elseif($pints_drunk<3) { print "Don't use the car, get on your bike\n"; } elseif($pints_drunk<=6) { print "Take a cab home\n"; } else { print "Call the local hospital!\n"; }

while() { } • while() { } executes a piece of code while the condition is true $count=0; while($count < 100) { print “ Пиво без водки -- деньги на ветер!<br/>"; $count=$count+1; # don't forget to increment $count! }

arrays • The variables we have looked at up until now are scalars. They can only contain one piece of data. • Arrays are variables that can contain one that one piece of data. • For example, a six pack in conveniently represented as an array of cans of beer. • For another example, a class is a group of people, each having a name, a social security number, etc.

numeric arrays • An numeric array has key value pairs where the keys are numbers. $good_beers[0]="Baltika 8"; $good_beers[1]="Bruch Festbock"; • or as follows $lousy_beers=array("Miller Lite", "Sam Adams", "Budweiser"); print $lousy_beers[0]; // prints: Miller Lite print $lousy_beers[2]; // prints: Budweiser

string arrays • Sometimes you need data structured by a string. For example for a price list. $price['Grosswald Export']=1.45; $price['Bruch Festbock']=1.74; // the array $price has strings as keys • An equivalent way to declare this is $price=array('Grosswald Export' => 1.45, 'Bruch Festbock' => 1.74);

array functions • There is a very large number of array functions. They are described in the array function reference. http://www.php.net/manual/en/ref.array.php • Now we are just looking at some examples.

count() • count() returns the size of an array $price['Grosswald Export']=1.45; $price['Bruch Festbock']=1.74; $product_number=count($price); print "We have $product_number products for you today."; // prints: We have 2 products for you today.

counting in numeric arrays • For numeric arrays, you can add members very simple without keeping track of number. $beers=("Karlsberg", "Bruch") ; $beers[]="Budweiser"; // $beer now has Karlberg, Bruch and Budweiser print count($beers) ; // prints 3

looping through an array • foreach() loops through an array. An example illustrates print "<table caption=\"price list\">\n"; foreach ($price as $item => $euro_amount) { print "<tr><td>$item</td>\n"; print "<td>€$euro_amount</td></tr>\n"; } print "</table>"; • This prints the full price list. But it could also do the whole form. This is fabulous!

example from the form • $_GET is an array. You can loop through it. foreach($_GET as $control => $value) { print “you set $control to $value<br/>\n”; }

the well-aligned price table $l_r=array('left','right'); $count=0; // counter of elements printed print "<table caption=\"price list\">\n"; foreach ($price as $item => $euro_amount) { print "<tr><td align=\"$l_r[$count % 2]\""; print "$item"; $count++; print "</td>\n<td align=$l_r[$count % 2]\"> €$euro_amount</td></tr>\n"; $count++; }

print "</table>\n"; • // This produces something like • // <table caption="price list"> • // <tr><td align="left">Grosswald Export</td> • // <td align="right">€1.45</td></tr> • // <tr><td align="left">Bruch Festbock</td> • // <td align="right"'>€1.74</td></tr> • // </table>

multiple arrays • Example $products[0]['name']="Grosswald Pilsener"; $products[0]['price']=1.56; $products[1]['name']="Grosswald Export"; $products[1]['price']=1.34; $products[2]['name']="Bruch Landbier"; $products[2]['price']=1.22;

restructure the shop • Instead of having two files, one with HTML, the other with PHP, let us have just one. It's easier. • One cool thing to help that is cool is $_SERVER[PHP_SELF] It gives the file name of your script in the form. As you change your script file name, you do not need to change the name of the form submitted.

check for submission • We include a hidden element in the form to see if it was submitted <input type="hidden" name="submitted" value="1"/> • We start the script we check for submission if($_GET['submitted']) { // work on the data that was submitted } else { // print form }

define some variables $form_greet='<h1>Please place your order</h1>'; $form_top="<form action=\"$_SERVER[PHP_SELF]\" method=\"GET\"><table>"; $form_submit='</table><input type="submit" value="I order"/>'; $submit_check='<input type="hidden" name="submitted" value="1"/>'; $form_bottom='</form>'; $order_head="<h1>Results of your order</h1><div>\n"; • $order_bottom="Thank you for your order. We will ship when we get your check. Prosit!\n</div>";

printing results if($_GET['submitted']) { $total_euro=0; print $order_head; foreach($_GET as $number => $amount) { if($amount > 0 and $products[$number]) { $pay=$amount*$products[$number][price]; print "$amount bottles of "; print $products[$number][name]; print " is €$pay<br/>"; $total_euro+=$pay; } }

print results, start form printing part $total_dollar=$total_euro*$euro_rate; $total_dollar=number_format($total_dollar,2); print "The euro rate is $euro_rate<br/>\n"; print "Your bill is \$$total_dollar\n</div>"; } else { // print the form print $form_greet; print $form_top; $product_count=0; foreach ($products as $prod) { print "\n<tr><td>"; print $prod['name']; print "</td><td>";

final part, printing the form print "<input type=\"text\" name=\""; print $product_count; print "\" maxlength=\"2\" size=\"2\"/>"; print "</td><td>@€"; print $prod['price']; print "</td></tr>\n"; $product_count++; // don't forget! } print $submit_check; print $form_submit; print $form_bottom; }

databases • Databases are collection of data with some organization to them. • The classic example is the relational database. • But not all database need to be relational databases.

relational databases • A relational database is a set of tables. There may be relations between the tables. • Each table has a number of record. Each record has a number of fields. • When the database is being set up, we fix • the size of each field • relationships between tables

problem with this database • All data wrong, but this is just for illustration. • Name covered inconsistently. There is no way to find films by Woody Allan without having to go through all spelling variations. • Mistakes are difficult to correct. We have to wade through all records, a masochist’s pleasure.

Better movie database ID | title | director | year M1 | Gone with the wind | D1 | 1963 M2 | Room with a view | D1 | 1985 M3 | High Noon | D2 | 1974 M4 | Star Wars | D3 | 1993 M5 | Alien | D2 | 1987 M6 | Blowing in the Wind | D3 | 1962 ID | director name | birth year D1 | Ford Coppola, Francis | 1942 D2 | Allan, Woody | 1957 D3 | Spielberg, Steven | 1942

Relational database • We have a one to many relationship between directors and film • Each film has one director • Each director has produced many films • Here it becomes possible for the computer • To know which films have been directed by Woody Allen • To find which films have been directed by a director born in 1942

LIS651 lecture 1 PHP basics , database introduction