Introduction to PHP

Transcript Introduction to PHP

Introduction to PHP
PHP
• PHP is the Hypertext Pre-processor
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Script language
Embedded into HTML
Runs as Apache module
Can use DB (MySQL, Oracle, Microsoft SQL,
PostgreSQL)
– Rich features: XML, PDF, IMAP, LDAP
PHP Origins
Rasmus Lerdorf (born Greenland, ed Canada)
PHP originally abbreviates for ‘Personal Home Pages’, now
‘PHP Hypertext Processor’
Other key developers: Zeev Surashi and Andi Gutmans
(Israel)
Open Source
PHP version 4.4.3 current at UWE
Due to upgrade to PHP 5
Scripting languages
• A scripting language is:
– often evolved not designed
– cross-platform since interpreter is easy to port
– designed to support a specific task – PHP -> Web
support
– un-typed variables (but values are typed)
– implicit variable declaration
– implicit type conversion
– stored only as script files
– compiled on demand
– may run on the server (PHP) or the client (Javascript)
PHP details
• Procedural language
– Compare with Javascript which is event-driven
• C-like syntax - { } ;
• Extensive Function Library
• Good Web-server integration
– Script embedded in HTML
– Easy access to form data and output of HTML pages
• Not fully object-oriented
– Java is fully object oriented – all functions have to be
in a class
– In PHP, classes are additional but quite simple to use
PHP and HTML
• HTML-embedded
– PHP scripts are essentially HTML pages with the
occasional section of PHP script.
– PHP script is enclosed in the tag pair:
<?php echo “hello” ?>
C-like language
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Free format - white space is ignored
Statements are terminated by semi-colon ;
Statements grouped by { … }
Comments begin with // or a set of comments /* */
Assignment is ‘=’ $a=6
Relational operators are ,< , > == ( not a single equal)
• Control structures include if (cond) {..} else { }, while
(cond) { .. } , for(startcond; increment; endcond) { }
• Arrays are accessed with [ ] : $x[4] is the 5th element
of the array $x – indexes start at 0
• Associative Arrays (hash array in Perl, dictionary in
Java) are accessed in the same way: $y[“fred”]
• Functions are called with the name followed by
arguments in a fixed order enclosed in ( ) :
substr(“fred”,0,2)
• Case sensitive - $fred is a different variable to $FRED
Function library
• Basic tasks
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String Handling
Mathematics – random numbers, trig functions..
Regular Expressions
Date and time handling
File Input and Output
• And more specific functions for– Database interaction –
• MySQL, Oracle, Postgres, Sybase, MSSQL ..
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Encryption
Text translation
Image creation
XML
String Handling
• String literals (constants) enclosed in double quotes “ ”
or single quotes ‘ ’
• Within “”, variables are replaced by their value: – called
variable interpolation. “My name is $name, I think”
• Within single quoted strings, interpolation doesn’t occur
• Strings are concatenated (joined end to end) with the
dot operator “key”.”board” == “keyboard”
• Standard functions exist: strlen(), substr() etc
• Values of other types can be easily converted to and
from strings – numbers implicitly converted to strings in a
string context.
• Regular expressions be used for complex pattern
matching.
Learning PHP
• Start with just the basics, installing a script to output an
HTML page
• Understand how PHP supports interaction with the
Browser or other clients
• Understand how PHP supports integration with
databases – Postgress
Basic PHP Syntax
<?php
?>
Datatypes
• String
– 'My name is Taro Keio.'
– "My name is $name."
• Boolean
– true
– false
• Integer
– 100
– 0x1c
• Floating point
• Array
– array("tokyo", "hanoi", "london")
– array("japan" => "tokyo", "vietnam" => "hanoi",
"england" => "london")
– $a[2]
– $a["vietnam"]
Variables in PHP
• All variables in PHP start with a $ sign symbol.
• Variables may contain strings, numbers, or
arrays.
<html>
<body>
<?php $txt="Hello World";
</body>
</html>
echo $txt;
?>
Variable Naming Rules
• A variable name must start with a letter or an underscore
"_"
• A variable name can only contain alpha-numeric
characters and underscores (a-Z, 0-9, and _ )
• A variable name should not contain spaces. If a variable
name should be more than one word, it should be
separated with underscore ($my_string), or with
capitalization ($myString)
Comments in PHP
<html>
<body>
<?php
//This is a comment
/*This is a comment block*/
?>
</body>
</html>
The If...Else Statement
Syntax
if (condition)
code to be executed if condition is true;
else
code to be executed if condition is false;
Example
<html>
<body>
<?php
$d=date("D");
if ($d=="Fri")
echo "Have a nice weekend!";
else
echo "Have a nice day!";
?>
</body>
</html>
The Switch Statement
Syntax
switch (expression)
{
case label1: code to be executed if expression = label1;
break;
case label2: code to be executed if expression = label2;
break;
default:
code to be executed if expression is
different from both label1 and label2;
}
Looping
• while - loops through a block of code if and as long as a
specified condition is true
• do...while - loops through a block of code once, and
then repeats the loop as long as a special condition is
true
• for - loops through a block of code a specified number of
times
• foreach - loops through a block of code for each
element in an array
The while Statement
Syntax
while (condition)
code to be executed;
The do...while Statement
Syntax
Do
{
code to be executed;
}
while (condition);
The for Statement
Syntax
for (initialization; condition; increment)
{
code to be executed;
}
The foreach Statement
Syntax
foreach (array as value)
{
code to be executed;
}
PHP Function
<html>
<body>
<?php
function writeMyName()
{
echo "Kai Jim Refsnes";
}
writeMyName();
?>
</body>
</html>
PHP Form Handling
<html>
<body>
<form action="welcome.php" method="post">
Name: <input type="text" name="name" />
Age: <input type="text" name="age" />
<input type="submit" />
</form>
</body>
</html>
welcome.php
<html>
<body>
Welcome <?php echo $_POST["name"]; ?>.
<br />
You are <?php echo $_POST["age"]; ?> years old.
</body>
</html>

Introduction to PHP

Transcript Introduction to PHP

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