Introducation to php for beginners

 Not to teach everything about PHP, but provide the basic knowledge  Explain code of examples  Provide some useful references

 PHP == ‘Hypertext Preprocessor’  Open-source, server-side scripting language  Used to generate dynamic web-pages  PHP scripts reside between reserved PHP tags ◦ This allows the programmer to embed PHP scripts within HTML pages

 Interpreted language, scripts are parsed at run-time rather than compiled beforehand  Executed on the server-side  Source-code not visible by client ◦ ‘View Source’ in browsers does not display the PHP code  Various built-in functions allow for fast development  Compatible with many popular databases

 Structurally similar to C/C++  Supports procedural and object-oriented paradigm (to some degree)  All PHP statements end with a semi-colon  Each PHP script must be enclosed in the reserved PHP tag <?php … ?>

 Standard C, C++, and shell comment symbols // C++ and Java-style comment # Shell-style comments /* C-style comments These can span multiple lines */

 PHP variables must begin with a “$” sign  Case-sensitive ($Foo != $foo != $fOo)  Global and locally-scoped variables ◦ Global variables can be used anywhere ◦ Local variables restricted to a function or class  Certain variable names reserved by PHP ◦ Form variables ($_POST, $_GET) ◦ Server variables ($_SERVER) ◦ Etc.

<?php $foo = 25; // Numerical variable $bar = “Hello”; // String variable $foo = ($foo * 7); // Multiplies foo by 7 $bar = ($bar * 7); // Invalid expression ?>

 The PHP command ‘echo’ is used to output the parameters passed to it ◦ The typical usage for this is to send data to the client’s web-browser  Syntax ◦ void echo (string arg1 [, string argn...]) ◦ In practice, arguments are not passed in parentheses since echo is a language construct rather than an actual function

 Notice how echo ‘5x5=$foo’ outputs $foo rather than replacing it with 25  Strings in single quotes (‘ ’) are not interpreted or evaluated by PHP  This is true for both variables and character escape-sequences (such as “n” or “”) <?php $foo = 25; // Numerical variable $bar = “Hello”; // String variable echo $bar; // Outputs Hello echo $foo,$bar; // Outputs 25Hello echo “5x5=”,$foo; // Outputs 5x5=25 echo “5x5=$foo”; // Outputs 5x5=25 echo ‘5x5=$foo’; // Outputs 5x5=$foo ?>

 $a - $b // subtraction  $a * $b // multiplication  $a / $b // division  $a += 5 // $a = $a+5 Also works for *= and /= <?php $a=15; $b=30; $total=$a+$b; Print $total; Print “<p><h1>$total</h1>”; // total is 45 ?>

 Use a period to join strings into one. <?php $string1=“Hello”; $string2=“PHP”; $string3=$string1 . “ ” . $string2; Print $string3; ?> Hello PHP

 If the string has a set of double quotation marks that must remain visible, use the [backslash] before the quotation marks to ignore and display them. <?php $heading=“”Computer Science””; Print $heading; ?> “Computer Science”

PHP Control StructuresPHP Control Structures  Control Structures: Are the structures within a language that allow us to control the flow of execution through a program or script.  Grouped into conditional (branching) structures (e.g. if/else) and repetition structures (e.g. while loops).  Example if/else if/else statement: if ($foo == 0) { echo ‘The variable foo is equal to 0’; } else if (($foo > 0) && ($foo <= 5)) { echo ‘The variable foo is between 1 and 5’; } else { echo ‘The variable foo is equal to ‘.$foo; }

 If (condition) { Statements; } Else { Statement; } <?php If($user==“John”) { Print “Hello John.”; } Else { Print “You are not John.”; } ?> No THEN in PHP

 While (condition) { Statements; } <?php $count=0; While($count<3) { Print “hello PHP. ”; $count += 1; // $count = $count + 1; // or // $count++; ?> hello PHP. hello PHP. hello PHP.

$datedisplay=date(“yyyy/m/d”); Print $datedisplay; # If the date is April 1st , 2009 # It would display as 2009/4/1 2009/4/1 $datedisplay=date(“l, F m, Y”); Print $datedisplay; # If the date is April 1st , 2009 # Wednesday, April 1, 2009 Wednesday, April 1, 2009

M Jan F January m 01 n 1 Day of Month d 01 Day of Month J 1 Day of Week l Monday Day of Week D Mon

 Functions MUST be defined before then can be called  Function headers are of the format ◦ Note that no return type is specified  Unlike variables, function names are not case sensitive (foo(…) == Foo(…) == FoO(…)) function functionName($arg_1, $arg_2, …, $arg_n)

<?php // This is a function function foo($arg_1, $arg_2) { $arg_2 = $arg_1 * $arg_2; return $arg_2; } $result_1 = foo(12, 3); // Store the function echo $result_1; // Outputs 36 echo foo(12, 3); // Outputs 36 ?>

Include “opendb.php”; Include “closedb.php”; This inserts files; the code in files will be inserted into current code. This will provide useful and protective means once you connect to a database, as well as for other repeated functions. Include (“footer.php”); The file footer.php might look like: <hr SIZE=11 NOSHADE WIDTH=“100%”> <i>Copyright © 2008-2010 KSU </i></font><br> <i>ALL RIGHTS RESERVED</i></font><br> <i>URL: http://www.kent.edu</i></font><br>

PHP - FormsPHP - Forms •Access to the HTTP POST and GET data is simple in PHPAccess to the HTTP POST and GET data is simple in PHP •The global variables $_POST[] and $_GET[] contain theThe global variables $_POST[] and $_GET[] contain the request datarequest data <?php if ($_POST["submit"]) echo "<h2>You clicked Submit!</h2>"; else if ($_POST["cancel"]) echo "<h2>You clicked Cancel!</h2>"; ?> <form action="form.php" method="post"> <input type="submit" name="submit" value="Submit"> <input type="submit" name="cancel" value="Cancel"> </form>

WHY PHP – Sessions ?WHY PHP – Sessions ?Whenever you want to create aWhenever you want to create a websitewebsite that allows you to store and displaythat allows you to store and display information about a user, determine which user groups a person belongs to,information about a user, determine which user groups a person belongs to, utilize permissions on yourutilize permissions on your websitewebsite or you just want to do something cool onor you just want to do something cool on your site,your site, PHP's SessionsPHP's Sessions are vital toare vital to eacheach of these features.of these features. Cookies are about 30% unreliable right now and it's getting worse every day.Cookies are about 30% unreliable right now and it's getting worse every day. More and more web browsers are starting to come with security and privacyMore and more web browsers are starting to come with security and privacy settings and people browsing the net these days are starting to frown uponsettings and people browsing the net these days are starting to frown upon Cookies because they store information on their local computer that they doCookies because they store information on their local computer that they do not want stored there.not want stored there. PHP has a great set of functions that can achieve the same results ofPHP has a great set of functions that can achieve the same results of Cookies and more without storing information on the user's computer. PHPCookies and more without storing information on the user's computer. PHP Sessions store the information on the web server in a location that you choseSessions store the information on the web server in a location that you chose in special files. These files are connected to the user's web browser via thein special files. These files are connected to the user's web browser via the server and a special ID called a "Session ID". This is nearly 99% flawless inserver and a special ID called a "Session ID". This is nearly 99% flawless in operation and it is virtually invisible to the user.operation and it is virtually invisible to the user.

PHP - SessionsPHP - Sessions •Sessions store their identifier in a cookie in the client’s browserSessions store their identifier in a cookie in the client’s browser •Every page that uses session data must be proceeded by theEvery page that uses session data must be proceeded by the session_start()session_start() functionfunction •Session variables are then set and retrieved by accessing the globalSession variables are then set and retrieved by accessing the global $_SESSION[]$_SESSION[] •Save it asSave it as session.phpsession.php <?php<?php session_start();session_start(); if (!$_SESSION["count"])if (!$_SESSION["count"]) $_SESSION["count"] = 0;$_SESSION["count"] = 0; if ($_GET["count"] == "yes")if ($_GET["count"] == "yes") $_SESSION["count"] = $_SESSION["count"] + 1;$_SESSION["count"] = $_SESSION["count"] + 1; echo "<h1>".$_SESSION["count"]."</h1>";echo "<h1>".$_SESSION["count"]."</h1>"; ?>?> <a href="session.php?count=yes">Click here to count</a><a href="session.php?count=yes">Click here to count</a> http://www.cs.kent.edu/~nruan/session.php

Avoid Error PHP - SessionsAvoid Error PHP - Sessions PHP Example: <?php echo "Look at this nasty error below:<br />"; session_start(); ?> Error! PHP Example: <?php session_start(); echo "Look at this nasty error below:"; ?> Correct Warning: Cannot send session cookie - headers already sent by (output started at session_header_error/session_error.php:2) in session_header_error/session_error.php on line 3 Warning: Cannot send session cache limiter - headers already sent (output started at session_header_error/session_error.php:2) in session_header_error/session_error.php on line 3

Destroy PHP - SessionsDestroy PHP - Sessions Destroying a Session why it is necessary to destroy a session when the session will get destroyed when the user closes their browser. Well, imagine that you had a session registered called "access_granted" and you were using that to determine if the user was logged into your site based upon a username and password. Anytime you have a login feature, to make the users feel better, you should have a logout feature as well. That's where this cool function called session_destroy() comes in handy. session_destroy() will completely demolish your session (no, the computer won't blow up or self destruct) but it just deletes the session files and clears any trace of that session. NOTE: If you are using the $_SESSION superglobal array, you must clear the array values first, then run session_destroy. Here's how we use session_destroy():

Destroy PHP - SessionsDestroy PHP - Sessions <?php // start the session session_start(); header("Cache-control: private"); //IE 6 Fix $_SESSION = array(); session_destroy(); echo "<strong>Step 5 - Destroy This Session </strong><br />"; if($_SESSION['name']){ echo "The session is still active"; } else { echo "Ok, the session is no longer active! <br />"; echo "<a href="page1.php"><< Go Back Step 1</a>"; } ?>

PHP OverviewPHP Overview  Easy learning  Syntax Perl- and C-like syntax. Relatively easy to learn.  Large function library  Embedded directly into HTML  Interpreted, no need to compile  Open Source server-side scripting language designed specifically for the web.

 Conceived in 1994, now used on +10 million web sites.  Outputs not only HTML but can output XML, images (JPG & PNG), PDF files and even Flash movies all generated on the fly. Can write these files to the file system.  Supports a wide-range of databases (20+ODBC).  PHP also has support for talking to other services using protocols such as LDAP, IMAP, SNMP, NNTP, POP3, HTTP.

 Save as sample.php: <!– sample.php --> <html><body> <strong>Hello World!</strong><br /> <?php echo “<h2>Hello, World</h2>”; ?> <?php $myvar = "Hello World"; echo $myvar; ?> </body></html> First PHP scriptFirst PHP script

 Function: list all tables in your database. Users can select one of tables, and show all contents in this table.  second.php  showtable.php

<html><head><title>MySQL Table Viewer</title></head><body> <?php // change the value of $dbuser and $dbpass to your username and password $dbhost = 'hercules.cs.kent.edu:3306'; $dbuser = 'nruan'; $dbpass = ‘*****************’; $dbname = $dbuser; $table = 'account'; $conn = mysql_connect($dbhost, $dbuser, $dbpass); if (!$conn) { die('Could not connect: ' . mysql_error()); } if (!mysql_select_db($dbname)) die("Can't select database");

$result = mysql_query("SHOW TABLES"); if (!$result) { die("Query to show fields from table failed"); } $num_row = mysql_num_rows($result); echo "<h1>Choose one table:<h1>"; echo "<form action="showtable.php" method="POST">"; echo "<select name="table" size="1" Font size="+2">"; for($i=0; $i<$num_row; $i++) { $tablename=mysql_fetch_row($result); echo "<option value="{$tablename[0]}" >{$tablename[0]}</option>"; } echo "</select>"; echo "<div><input type="submit" value="submit"></div>"; echo "</form>"; mysql_free_result($result); mysql_close($conn); ?> </body></html>

<html><head> <title>MySQL Table Viewer</title> </head> <body> <?php $dbhost = 'hercules.cs.kent.edu:3306'; $dbuser = 'nruan'; $dbpass = ‘**********’; $dbname = 'nruan'; $table = $_POST[“table”]; $conn = mysql_connect($dbhost, $dbuser, $dbpass); if (!$conn) die('Could not connect: ' . mysql_error()); if (!mysql_select_db($dbname)) die("Can't select database"); $result = mysql_query("SELECT * FROM {$table}"); if (!$result) die("Query to show fields from table failed!" . mysql_error());

$fields_num = mysql_num_fields($result); echo "<h1>Table: {$table}</h1>"; echo "<table border='1'><tr>"; // printing table headers for($i=0; $i<$fields_num; $i++) { $field = mysql_fetch_field($result); echo "<td><b>{$field->name}</b></td>"; } echo "</tr>n"; while($row = mysql_fetch_row($result)) { echo "<tr>"; // $row is array... foreach( .. ) puts every element // of $row to $cell variable foreach($row as $cell) echo "<td>$cell</td>"; echo "</tr>n"; } mysql_free_result($result); mysql_close($conn); ?> </body></html>

 mysql_connect() mysql_select_db()  include()  mysql_query() mysql_num_rows()  mysql_fetch_array() mysql_close()

 PHP began in 1995 when Rasmus Lerdorf developed a Perl/CGI script toolset he called the Personal Home Page or PHP  PHP 2 released 1997 (PHP now stands for Hypertex Processor). Lerdorf developed it further, using C instead  PHP3 released in 1998 (50,000 users)  PHP4 released in 2000 (3.6 million domains). Considered debut of functional language and including Perl parsing, with other major features  PHP5.0.0 released July 13, 2004 (113 libraries>1,000 functions with extensive object-oriented programming)  PHP5.0.5 released Sept. 6, 2005 for maintenance and bug fixes

 Larry Ullman’s books from the Visual Quickpro series  PHP & MySQL for Dummies  Beginning PHP 5 and MySQL: From Novice to Professional by W. Jason Gilmore ◦ (This is more advanced and dense than the others, but great to read once you’ve finished the easier books. One of the best definition/description of object oriented programming I’ve read)

Introducation to php for beginners

More Related Content

What's hot

Viewers also liked

Similar to Introducation to php for beginners

Recently uploaded

Introducation to php for beginners