Post on 27-Mar-2015
transcript
LIS651 lecture 1
PHP basics, database introduction
Thomas Krichel
2006-11-04
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 quotesprint 'She wrote: "I want beer." and sighed.';
// prints: She wrote: "I want beer." and sighed.
• and vice versaprint "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 strings, you should look at those string functions at
http://www.php.net/manual/en/ref.strings.php• Working with strings 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 $zip_length;
// hopefully, prints 5
strip_tags()
• strip_tags(string) removes HTML tags and their contents from the string string$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?
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 secondprint 10 % 7; // prints 3
• Use parenthesis for complicated calculations$pack=2 * (10 % 7);
print "a $pack pack"; // prints: a 6 pack
other number functions
• abs() calculates the absolute valueprint abs(-3) // prints: 3
print abs(3) // prints: 3
• The list of functions that use numbers is http://www.php.net/manual/en/ref.math.php
geeky increment/decrement
• ++ is an operator that adds one. The value of the resulting expression depends on the position of the operator$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 $brand="Sam Adams") {
echo "Commiserations for buying a lousy beer\n";
} # where is the mistake in this piece of code?
• ‘not’ or ‘!’ is Boolean NOT• These can be combined. Use parenthesis
if((($pints > 2) and ($vehicle=='car')) or (($pints > 6) and ($vehicle=='bicycle'))) {
print "order a cab!\n";
}
variable types
• Variables in PHP have types. You can check for typesis_numeric()
is_string()
is_int()
is_float()
• They all return a Boolean value.• They can be used to check the nature of a
variable.
if() { }
• if(expression) evaluates an expression expression as Boolean, and executes a block of code surrounded by curly brackets if the expression is true.if($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 falseif($sober) {
print "You can drive\n";
}
else {
print "Check if you are fit to drive\n";
}
elseif() { }• You can build chain of conditions
if($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=array("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 illustratesprint "<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
$_SERVER[PHP_SELF]
It gives the file name of your script in the form. As
you change your script file name, you do not need to change the name of the form submitted.
• We include a hidden element in the form to see if it was submitted<input type="hidden" name="submitted" value="1"/>
• We start the script we check for submissionif($_GET['submitted']) {
// work on the data that was submitted
}
else {
// print form
}
check for submission
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
example: Movie database
ID | title | director | date
M1 | Gone with the wind | F. Ford Coppola | 1963
M2 | Room with a view | Coppola, F Ford | 1985
M3 | High Noon | Woody Allan | 1974
M4 | Star Wars | Steve Spielberg | 1993
M5 | Alien | Allen, Woody | 1987
M6 | Blowing in the Wind | Spielberg, Steven | 1962
• Single table• No relations between tables, of course
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
Many-to-many relationships
• Each film has one director, but many actors star in it. Relationship between actors and films is a many to many relationship.
• Here are a few actorsID | sex | actor name | birth year
A1 | f | Brigitte Bardot | 1972
A2 | m | George Clooney | 1927
A3 | f | Marilyn Monroe | 1934
Actor/Movie table
actor id | movie id
A1 | M4
A2 | M3
A3 | M2
A1 | M5
A1 | M3
A2 | M6
A3 | M4
… as many lines as required
databases in libraries
• Relational databases dominate the world of structured data
• But not so popular in libraries– Slow on very large databases (such as catalogs)
– Library data has nasty ad-hoc relationships, e.g.• Translation of the first edition of a book
• CD supplement that comes with the print version
Difficult to deal with in a system where all relations and field have to be set up at the start, can not be changed easily later.
databases in web sites• Lots of active web sites are driven by relational
databases. All large active web sites are.• The design of a active web site first involves
looking at databases.• In a shop situation, we have the following tables
– customers– products– orders– orders_products
for multiple to multiple relationship between orders and products.
mySQL
• They are a very successful, open-source vendor of SQL software.
• Their product is basically freely available. • We will learn the mySQL dialect of SQL. • We will do this next week.
phpmyadmin
• phpmyadmin is a set of PHP scripts that create a general purpose interface to work with a mySQL database.
• It is written in PHP. • It lives at http://wotan.liu.edu/phpmyadmin.• You need an account. This is not your wotan
account, but a permission to use a database on the mySQL server running at wotan.
creating mySQL databases
• To create accounts however, I will do it in mySQL directly with you now. After logging into mySQL as the root user, I will issueCREATE DATABASE user_name;
GRANT ALL ON user_name.* TO user_name IDENTIFIED BY 'secret_word' WITH GRANT OPTION;
• user_name is your user name. It is the name of your database as well as the name under which you are logging in.
• You will type in the secret word.
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Thank you for your attention!
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