PHP Overview
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PHP Overview
CS3520
1
PHP
• PHP = PHP: Hypertext Preprocessor
• Server-side scripting language that may be embedded into
HTML
• One goal is to get PHP files to generate client-side code
• end up with HTML, CSS, JavaScript, other client-side code!
2
PHP --- and its output
PHP
<html>
<head>
<title> PHP Introduction </title>
</head>
<body>
This is HTML! <br />
<?php echo 'This is PHP! <br />'; ?>
</body>
</html>
Output
<html>
<head>
<title> PHP Introduction
</title>
</head>
<body>
This is HTML! <br />
This is PHP! <br />
</body>
</html>
3
More PHP
<html>
<head>
<title> PHP Introduction </title>
</head>
<body>
This is HTML! <br />
<?php
echo 'This is PHP! <br />'; // prints to screen
/*
Here's a longer
comment
that spans multiple
lines.
*/
?>
</body>
</html>
PHP tags: <?php and ?>
The echo command
single line comment ( // )
Multiple line comment (/* and */)
4
PHP file names and code
• End in php file extension (order.php, login.php …..)
• You start all PHP scripts with the <?php open tag and end the
tag after your code with ?> .
5
Variables
• PHP is a loosely-typed language
• Do not need to declare the type of a variable
• Type can change throughout the program
• Must start with a letter, can contain numbers, no blank spaces
• scope (unless defined as global) is the script block it appears inside
of.
$x = 42; // store the value 42 in $x
echo $x; // prints 42
echo $x+1; // prints 43, value of $x is still 42
$x = ‘hello!’ // type of $x can change
6
Longer example
<html>
<body>
<?php
// PHP variables always start with $.
$jake = 4;
$allen = 3 + $jake;
echo $jake, " ", $allen
?>
<hr>
Some html goes here....
<br>
<script language="php">
// This is another wayt to enter PHP. And variable values survive
between
// PHP regions.
echo '$jake has the value ', $jake, ".<br>";
</script>
<i>This is more HTML.</i>
<p>
<table>
<?php
// There are many pre-defined variables which describe the script's
// environment.
echo "<tr><td><b>My URL is:</b>:</td><td>http://",
$_SERVER["SERVER_NAME"], ":", $_SERVER["SCRIPT_NAME"], "</td></tr>";
echo "<tr><td><b>Your browser is</b>:</td><td>",
$_SERVER["HTTP_USER_AGENT"], "</td></tr>";
echo "<tr><td><b>Your IP address is</b>:</td><td>",
$_SERVER["REMOTE_ADDR"], "</td></tr>";
?>
</table></p>
</body>
</html>
7
Output previous example
47
Some html goes here....
$jake has the value 4.
This is more HTML.
My URL is::
http://puzzle.sci.csueastbay.edu:/~gre
we/PHP/phpvariables.php
Your browser is:
Mozilla/5.0 (Windows NT 6.3;
WOW64) AppleWebKit/537.36
(KHTML, like Gecko)
Chrome/42.0.2311.90 Safari/537.36
Your IP address is:
108.243.32.249
8
Constants
• Constants can be simply defined as follows
<?php
// Works as of PHP 5.3.0
const CONSTANT = 'Hello World';
echo CONSTANT;
?>
9
Some Pre-defined variables--see PHP documentation
• There are a number of pre-defined variables in PHP. See
http://php.net for a cmoplete listing. Below is a subset of
predefined variables/arrays :
• $GLOBALS
• $_SERVER
• $_GET
• $_POST
• $_FILES
• $_COOKIE
• $_SESSION
• $_REQUEST
• $_ENV
•
10
Arrays
• 2 kinds
• Indexed are numerically indexed starting from 0.
• Associative arrays associate keys to their values and are indexed by their
keys.
• The following are examples of two associative arrays, $a, $b defined
followed by a numerically index array, $c.
$a = array("a" => "apple", "b" => "banana");
$b = array("a" => "pear", "b" => "strawberry", "c" => "cherry");
$c = array("apple", "banana");
$a['b']; //will have the value banana
$c[1]; //will have the value of banana
11
Operations – similar to C++,
Java
• Arithmetic operators
• +, -, *, /, % (modulus – remainder after division)
• Logical AND (&&), OR (||), NOT (!)
• Assignment operators
• Shorthand for assignment operators:
• $x += $y equivalent to $x = $x + $y
• Also works with subtraction, multiplication, division, modulus,
and string concatenation
12
Equality: == OR ===
• Two “equality” operators
• == tests for “equality” in value but not necessarily type
• === tests for “identity” in value AND type
• == ignores the distinction between:
• Integers, floating point numbers, and strings containing the same
numerical value
• Nonzero numbers and boolean TRUE
• Zero and boolean FALSE
• Empty string, the string ‘0’ and boolean FALSE
• Any other non-empty string and boolean TRUE
13
Strings and operations
• Concatenation of strings – the . operator
$a = ‘hello’;
$b = ‘world’;
echo $a . ‘ ‘ . $b . ‘!’;
// prints ‘hello world!’
• String functions
• Length: strlen()
• Position of substring: strpos()
• More on string functions:
http://www.w3schools.com/php/php_ref_string.asp
14
Functions
• keyword funciton.
• no return type for a function
• parameters are defined without type
• In the first generic example, you see a function (myFunction) defined with n arguments and
the last line of code returns a value.
• You would simply call this function via:
$the_value = myFunction($a1,$a2,...$an);
• Defining the funciton
<?php
function myFunction($arg_1, $arg_2, /* ..., */ $arg_n)
{
echo "Example function.\n";
return $retval;
}
?>
15
Function with array as a
parameter
<?php function takes_array($input)
{
echo "$input[0] + $input[1] = ", $input[0]+$input[1];
}?>
16
Functions and arguments
• DEFAULT – pass by value
17
Functions and passing by
reference
• by default arguments are passed by value to a function. The
following code illustrates how to pass by reference:
<?php
function add_some_extra(&$string)
{ $string .= 'and something extra.'; }
//how to call the function above
$str = 'This is a string, ';
add_some_extra($str);
echo $str; // outputs 'This is a string, and something extra.'
?>
18
Functions with default
parameter values
<?php
function doit($type = "txt")
{
return "Default type is $type.\n";
}
//now lets use the function
echo doit();
echo doit(null);
echo doit("jpg");
?>
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