PHP Part 1

What is PHP?

developed since 1994, most update release is PHP4

PHP3, released in 1998, has gained rapid popularity
an open-source server-side scripting language
well supported by open-source developers
cross-platform, suitable for today's heterogeneous network environments.
design for creating dynamic Web pages for e-commerce and other Web applications
found on >5 million domains (according to survey in year 2001 by Netcraft, http://www.netcraft.com/survey/) at a growing rate up to 15% per month, available on over 36% of Apache Web servers

PHP - development

PHP keywords and function names are NOT case sensitive, while variable name ARE case sensitive

print("Hello world!"); and PRINT("Hello world!"); produce the same results

$num1 = 1; and $NUM1 = 1; are different

PHP commands can be embedded in the HTML page
similar syntax to C and Perl
easy-to-program scripting language
short development time
easy to maintain compare to Perl or ASP code
open source - bug are fixed, features added with no costs
open API - developer can add easy-to-program modules to extending the language
quicker response time
improved security
Web servers supporting PHP will

(1) scan an HTML file, by default
(2) pass HTML code to the browser as usual, up until the server happens upon a PHP line of code
(3) switches over to PHP mode in anticipation of a PHP command
(4) closes out the PHP mode
(5) resume its scanning in HTML mode.

Information flow of a server-side scripting language

PHP - compatibility

offers connectivity to common databases such as Oracle, Informix, MS SQL Server, Sybase, MySQL, ODBC...etc)
offers integration with various external libraries (e.g. generating PDF documents, parsing XML)
work well on Linux machines running Apache server, UNIX or Windows platform with Netscape or MS Web server software
features sub-second access times in combination PHP-Apache-Linux
supports HTTP sessions, Java connectivity

Embedding PHP code

<?php tag informs the server that PHP code is to follow
?> tag closes out the PHP code
The following 3 sample files produce the same output:
A plain HTML file, sample : hello.htm

<html>
<head><title>Plain HTML - hello.htm</title></head>
<body>Hello World!!</body>
</html>

In PHP code, sample : hello.php

<html>
<head><title>PHP - hello.php</title></head>
<body><?php echo "Hello World!!<p>";?></body>
</html>

PHP embedded within HTML, sample : hello-em.php

<html>
<head><title>PHP - hello-em.php</title></head>
<body><?php echo "Hello ";?>World!!<p></body>
</html>

Static web page vs Dynamic web page

Comments

PHP provides 3 different comment characters:

/* and */

/*　 for multiline comment.
But,　they　cannot　be　nested.
*/

//

//　a　single　line　comment
$num1　=　234;　//　A　single　line　comment
#

#　a　single　line　comment
$string1　=　"Hello World!!"　#　A　single　line　comment.
// and # single line comment characters allow to include comments from the comment character until the end of the line

Variable

is necessary to produce dynamic Web page

is prefixed by a dollar sign ($)

types in PHP:

Type	Description
Integer	integer number
Double	floating point number
bool	boolean (true of false)
Array	hybrid of ordered array and associative array
object	object with properties and methods

is auto-declared when assigning a value to it, formal declaration is not required
loosely typed, types can be changed during run-time

// PHP converts the variable real to string before passing it to the echo function
$real = 123.4;

echo $real;

In the statement
echo 100 + "100";
PHP:
- converts string 100 to an integer
- adds it to integer 100
- passes it to function echo, which will convert it to a string and display it
To cast a variable to a particular type, use
- cast operators
  $num = (string) 12;
- settype() function
  $num1 = 12; settype($num1, "double");
PHP arrays can be indexed from 0, by strings, with non-continuous numbers, by a mix of numbers and strings
sample: variables.php

<html><head><title>PHP samples</title></head>
<body>
<?php
$number = 5;
$string1 = "this is string 1\n";
$string2 = 'this is another "string"';
$real = 37.2;

$array1 = array(10, 20, 30, 40, 50);
$array2 = array("one" => 10, "two" => 20, "three" => 30);
$array3 = array(5 => "five", "six", "seven");

printf("number: %d; string1: %s; string2: %s; real: %6.2f", $number, $string1, $string2, $real);
?>
<p>

<table border="1" width="40%">
   <tr>
   <td width="40%">$array1[1]</td>
   <td width="60%"><?php print $array1[1];?></td>
   </tr>
   <tr>
   <td width="40%">$array2["one"]</td>
   <td width="60%"><?php print $array2["one"];?></td>
   </tr>
   <tr>
   <td width="40%">$array3[7]</td>
   <td width="60%"><?php print $array3[7];?></td>
   </tr>
</table>

</body></html>

Display on browser:

Built-in Variables

for accessing the Web server's environment, form/cookie data and PHP internals.

PHP Superglobals (from PHP4.1.0 onwards)

$GLOBALS - Contains a reference to every variable which is currently available within the global scope of the script. The keys of this array are the names of the global variables. $GLOBALS has existed since PHP 3.

$_SERVER

Variables set by the web server or directly related to the execution environment of the current script. Analogous to the old $HTTP_SERVER_VARS array (deprecated).

$_GET

Variables provided to the script via HTTP GET. Analogous to the old $HTTP_GET_VARS array (deprecated).

$_POST

Variables provided to the script via HTTP POST. Analogous to the old $HTTP_POST_VARS array (deprecated).

$_COOKIE

Variables provided to the script via HTTP cookies. Analogous to the old $HTTP_COOKIE_VARS array (deprecated).

$_FILES

Variables provided to the script via HTTP post file uploads. Analogous to the old $HTTP_POST_FILES array (deprecated).

$_ENV

Variables provided to the script via the environment. Analogous to the old $HTTP_ENV_VARS array (deprecated).

$_REQUEST

Variables provided to the script via any user input mechanism, and which therefore cannot be trusted.

$_SESSION

Variables which are currently registered to a script's session. Analogous to the old $HTTP_SESSION_VARS array (deprecated)
e.g. Apache Environment

View browser information by using $_SERVER["HTTP_USER_AGENT"] sample1a.php

Display on browser :

Mozilla/4.0 (compatible; MSIE 5.0; Windows 98; DigExt)

Note: $HTTP_USER_AGENT was used instead of $_SERVER["HTTP_USER_AGENT"] in previous version of PHP.

To view other variables set by your web server, phpinfo() sample1b.php

<html><head><title>PHP Test</title></head>
<body>
<?php
phpinfo();
?>
</body></html>

Display on browser :

PHP 4 Credits are follows:
Configuration PHP Core, Standard, ...ftp, mysql, odbc, ..,session, xml, wddx, apache, Apache Environment, HTTP Headers Information, Environment, PHP Variables

Conditionals and Looping

if and elseif
while loop
for loop

<?php
//　Conditionals
if　($a)　{
　　　　print　"a　is　true<BR>\n";
}　elseif　($b)　{
　　　　print　"b　is　true<BR>\n";
}　else　{
　　　　print　"neither　a　or　b　is　true<BR>\n";
}

//　Do-while Loops
do　{
　　　　$c　=　function1();
}　while　($c);

//　While Loops
while　($d)　{
　　　　print　"ok<BR>\n";
　　　　$d　=　function1();
}

for　($i　=　0;　$i　<　5;　$i++)　{
　　　　print　"i=$i<BR>\n";
}

?>

Sample : sample1c.php

<html><head><title>PHP Test</title></head>
<body>

<?php if (strstr($_SERVER["HTTP_USER_AGENT"],"MSIE")) {
?>
<center><b>You are using Internet Explorer</b></center>
<?
} else {
?>
<center><b>You are not using Internet Explorer</b></center>
<?
}
?>
</body></html>

Assignment, Equality and Identity

PHP defines 3 operation

= assigns a value to a variable
== compares the values of 2 operands
=== compares values and types of 2 operands
examples:

$num1 = 1;
$num2 = 1;
$num3 = "1";
($num1 == $num2) // true, they are equal
($num1 == $num3) // true, they are equal
($num1 === $num2) // true, they are identical
($num1 === $num3) // false, they are equal, but not identical.

Functions

passing arguments by value, values of arguments unchanged
to change values of arguments, pass arguments by reference by using '&' operator

function add10(&$x) { // pass by reference
$x = $x +10;
}
$x = 5;
echo $x; // prints '5'
add10($x);
echo $x; // prints '15'

function that returns values

function add10($x) {
return $x +10;
}
$before = 5;
$after = add10($before); // $after = '15'

Dealing with form

form element in a form will automatically result in a variable with the same name as the element being created on the target page
i.e. a variable "name" in a form will be set as $name by PHP automatically
Sample : sample2.htm

<html>
<head><title>PHP sample 2</title></head>

<body>

<p>Please input name and age: </p>
<form method="post" action="sample2.php">
<p>Your name: <input type="text" name="name"></p>
<p>You age: <input type="text" name="age"></p>

<p>
<input type="submit" name="Submit" value="Submit">
</p>

</form>
</body>
</html>

sample2.php

<html>

<head><title>PHP Sample 2</title></head>
<body>
Hi, <?php echo $_POST["name"]; ?>.
You are <?php echo $_POST["age"]; ?> years old.
</body>

</html>

Note: $name and $age was used instead of $_POST["name"] and $_POST["age"] in previous version of PHP.

Display on Browser if "Chan Tai Man" and "18" are input as name and age with respectively:

Hi, Chan Tai Man. You are 18 years old.

References

http://conf.php.net/
http://www.zend.com/zend/art/intro.php
http://www.phpbuilder.com/
http://www.php.net/
http://www.zend.com/zend/tut/ (many useful examples)
http://www.mysql.com/