php & gdbm tutorial - v3 - dalhousie...
TRANSCRIPT
PHP & GDBM Tutorial
By Naureen Nizam
May 17, 2011
Agenda
Introduction on PHP
PHP 101 – Examples
Introduction on GDBM
Using PHP & GDBM
Example
Resources
Questions
Introduction to PHP
PHP: Hypertext Preprocessor
Created by Rasmus Lerdorf in 1995
Scripting language - server-side webdevelopment Dynamic Web Pages
Command line scripting
Client-side GUI applications
Open Source
Comparable to ASP
What can it do?
Dynamic generation of web-page content
Database interaction
Processing of user supplied data
File handling
Text processing
Network interaction
…
PHP 101
PHP is embedded within HTML pageswith tags: <?php … ?>
PHP 101 (cont’d)
Each line must be terminated by asemi-colon.
Literals: All strings must be enclosed in single of
double quotes: ‘Hello’ or “Hello”.
Numbers are not in enclosed in quotes: 1or 45 or 34.564
Booleans (true/flase) can be writtendirectly as true or false.
PHP 101 (cont’d)
Comments:
// This is a comment
# This is also a comment
/* This is a commentthat is spread overmultiple lines */
PHP 101 (cont’d)
Displaying Data
Two language constructs: print() and echo()
Can be used with or without brackets.
<?php
echo ‘Hello World!<br />’;echo(‘Hello World!<br />’);
print ‘Hello World!<br />’;print(‘Hello World!<br />’);
?>
PHP 101 (cont’d)
Escaping Characters
Some characters are considered ‘special’
Escape these with a backslash \
Example: echo ‘Claire O\’Reilly ’;
PHP 101 (cont’d)
Variables
Need a place to store a value (string,number, etc.)
Naming: $ followed by variable name
(must start with a letter or an underscore)
Case sensitive $variable differs from $Variable
PHP 101 (cont’d)
<?php$name = ‘John’;$age = 28;echo $name;echo ’ is ‘;echo $age;// John is 28?>
Example
PHP 101 (cont’d)
Constants (unchangeable variables) are definedusing the define() function. By convention, constant names are usually in
UPPERCASE.<?phpdefine(‘NAME’,‘John’);define(‘AGE’,28);echo NAME;echo ’ is ‘;echo AGE;// John is 28?>
PHP 101 (cont’d)
Statements IF statement
if (<condition>) {
//php code goes here
}
else {
//php code goes here
}
For loop
for($i=0;$i < 10;$++i) {echo(“the value is :”. $i);
}
PHP 101 (cont’d)
Functions
function my_func(<parameters>) {
//do something in the function
}
PHP 101 (cont’d)
Arrays each element has a value, data stored in the
element.
And has a key by which the element can bereferred to. $staff[] = “Jack”;
$staff[] = “John”;
OR
$staff = array (“Jack”, “John”);
Print: print_r($staff);
PHP 101 (cont’d)
Useful functions: sort(); //sort an array (lowest to highest) count(); //counts all the elements in an array split(); // split string into an array by regular expression array_push(); //push one or more elements to the end of the array trim(); //strip whitespaces from beginning and end of a string unset(); //unset a given variable isset(); //determine if a variable is set and is not NULL explode(); //split a string by string into an array implode(); //join array elements with a string preg_match(); //perform a regular expression match preg_replace(); //perform a regular expression match $fh = fopen($File, 'r') or exit("Unable to open file!");
Introduction to GDBM
GNU Database Manager Database routines Use extensive hashing Implementation of a key->value database The five basic functions of gdbm:
gdbm_open (open a database) gdbm_store (store a key,value pair in a database) gdbm_fetch (given a key get the associated value from
the database) gdbm_delete (delete a key,value pair from the
database) gdbm_close (close a database)
Using PHP and GDBM
PHP must be compiled with GDBMenabled (DBA module) on the server ./configure …' '--with-gdbm' '—
DBA support => enabled
Supported handlers => gdbm
bluenose.cs.dal.ca (Done)
hector.cs.dal.ca (Pending - this week)
Verify using <?php phpinfo(); ?>
Steps
1. Open databaseCreate: $dbh= dba_open('cars.db', 'c', 'gdbm')Read: $dbh= dba_open(‘cars.db','r','gdbm');
2. Insert into the databasedba_insert($key, $value, $dbh);
3. Retrieve values from the databasedba_fetch($key, $dbh); //to fetch a specific keydba_firstkey($dbh); //to fetch the first keydba_nextkey($dbh); //to fetch the next keydba_delete("key", $dbh); //to delete a specific keydba_exists("key", $id); //to see if the key exist
4. Close Databasedba_close($dbh);
Example: PHP & GDBM
<?php
$dbh= dba_open('cars.db', 'c', 'gdbm') or die($php_errormsg);
//insert data$index=0;$value="Honda";dba_insert($index, $value, $dbh);
$index=1;$value="Toyota";dba_insert($index, $value, $dbh);
for ($key = dba_firstkey($dbh); $key !== false; $key = dba_nextkey($dbh)){
$value = dba_fetch($key, $dbh);print "$key: $value\n";
}
dba_close($dbh);?>
Create file [filename].php
Example (cont’d)
Make sure file is executable
Run file from command line
php [filename].php
A binary file called cars.db should becreated
Resources
