to get the file

Lecture 6.
PHP: Part 1
1

Origins and Uses of PHP
• Developed by Rasmus Lerdorf, a member of the Apache
Group, in 1994 to track visitors to his Web site
• PHP‟s development was transferred to a small group of
devoted volunteers and now is an open-source product
• PHP is originally an acronym for Personal Home Page, later
PHP: Hypertext Preprocessor
• PHP, as a server-side scripting language, is used for form
handling, file processing, and database access
• has driver support for 15 database systems
• supports electronic mail protocols POP3 and IMAP
• supports distributed object architectures COM and CORBA
2

Overview of PHP
• PHP is a server-side scripting language whose scripts are
embedded in HTML documents
• Similar to JavaScript, but on the server side
• PHP is an alternative to CGI, Active Server Pages (ASP),
and Java Server Pages (JSP)
• Filename extension is .php, .php3, or .phtml
• PHP syntax is similar to that of JavaScript
• PHP is dynamically typed
• PHP has an extensive library of functions, making a flexible
and powerful
• http://www.php.net
3

Overview of PHP
• The PHP processor has two modes: copy (XHTML) and
interpret (PHP).
• PHP processor takes a PHP document as input and
produces an XHTML document file
• When it finds XHTML code in the input file, simply
copies it to the output file
• When it finds PHP script, it interprets it and send any
output of the script to the output file
• This new output file is sent to the requesting browser.
• The client never sees the PHP script.
4

Operation Overview
Web browser
Client
Request
a page
Transfer
XHTML file
Request
data
processing
Web Server
Generate
XHMTL file
Other
Server
Platform
PHP Engine
DB
5

General Syntactic Characteristics
• PHP code can be specified in an HTML document
internally or externally:
Internally:
Externally: include ("myScript.inc")
• The included file can contain XHTML or client-side
script as well as PHP
• If the file has PHP, the PHP must be in ,
even if the include appears in
6

General Syntactic Characteristics
• All variable names begin with $
• The name part is like the names of variables in many
programming languages: a letter or an underscore
followed by any number of letters, digits, or underscores
• PHP variables are case sensitive, but reserved words
and function names are not. (Table 12.1)
(Ex) while, WHILE, While, and wHiLe are same
• Comments - three different kinds (Java and Perl)
(a) // ... ; for single line
(b) # ... ; for single line
(c) /* ... */ ; for multiple-line
7

PHP Reserved Words
and else function not this
break elseif global or true
case extends if require var
class false include return virtual
continue for list static xor
default foreach new switch while
do
8

General Syntactic Characteristics
• PHP statements are terminated with semicolons.
• Compound statements for control structures are
formed with braces
• Unless used as the body of a function definition,
compound statements cannot be blocks
• They cannot define locally scoped variables
9

Example
10

PHP TYPES
• Four scalar types
• Boolean
• Integer
• Double
• String
• Two compound types
• Array
• Object *
• Two special types
• NULL
• Resource *
* will not be covered here.
11

Variables
• There are no type declarations because of dynamic typing
• The type of a variable is set every time it is assigned a value
• An unassigned ( unbound ) variable has the value, NULL
• A variable of NULL in the expression will be coerced to a value
dictated by the context of the use
(Ex) If a number, NULL is coerced to 0
If a string, NULL is coerced to the empty string
• The unset function sets a variable to NULL
• The IsSet function tests whether a variable is NULL
(Ex) IsSet ( $fruit ) returns TRUE if $fruit has non-NULL value
12

Variables
• If you prefer to be informed when an unbound variable
is referenced, place the error_reporting(15) at the
beginning of the script in the document file
• The error_reporting function is used to change the error –
reporting level of the PHP interpreter
• The default error-reporting level is 7
• PHP has many predefined variables, including the
environment variables of the host operating system
• You can get a list of the predefined variables by
calling phpinfo() in a script
13

primitive types
• Integer type corresponds to the long type of C and its
successors
• Double type corresponds to the double type of C and
its successors. Decimal point, an exponent, or both.
• There is no character type
• A single character data value is a string of length one
• Strings
• Characters are single bytes
• String literals use single (′)or double quotes(″)
14

Example
• Integer
$var = 1234;
$var = -1234;
$var = 01234;
$var = 0x1234;
// Decimal
// Decimal
// Octal
// Hexadecimal
• Floating point
$a = 1.234; // Float
$a = 0.1234e1; // Exponential
15

String
• Single-quoted string literals
• Embedded variables are NOT interpolated
(Ex) „The sum is: $sum‟ = The sum is: $sum
• Embedded escape sequences are NOT recognized
• Double-quoted string literals
• Embedded variables ARE interpolated
(Ex) “The sum is: $sum” = The sum is: 12.4
• If there is a variable name in a double-quoted string but
you don‟t want it interpolated, it must be backslashed
• Embedded escape sequences ARE recognized
• For both single- and double-quoted literal strings,
embedded delimiters must be backslashed
16

Special character
Special char.
\n
\r
\t
\\
\$
\”
Semantics
new line
Return carriage
Tab
Backslash
Dollar
Quotation mark
17

Boolean
• The only two possible values are TRUE and FALSE
(case insensitive)
• If an integer expression is used in Boolean context, it
is FALSE if it is zero; otherwise, it is TRUE.
• If a string expression is used in Boolean context, it is
FALSE if it is either the empty string or the string "0";
otherwise, it is TRUE.
18

Arithmetic Operators and Expressions
• +, -, *, /, %, ++, --
• For +,- and *, if either operand is double, then it
produces a double result
• If the result of integer division is not an integer, a
double is returned
• Any integer operation that results in overflow produces
a double
• The modulus operator (%) coerces its non-integer
operands to integer
19

Predefined Functions
Functi
on
Paramet
er
Returns
floor Double Largest integer less than or equal to the parameter
ceil
Double
round Double Nearest integer
srand Integer
rand
abs
min
Two
numbers
Integer or
double
Numbers Smallest
Smallest integer greater than or equal to the
parameter
Initializes a random number generator with the
parameter
A pseudorandom number greater than the first
parameter and smaller than the second
Absolute value of the parameter
max
Numbers Largest
20

String Operations and Functions
• The only operator is period(.) for catenation
• String variables can be treated like arrays for access to
individual characters
• The position can be specified in braces
(Ex) If $str has “apples”, $str{3} is the fourth (l)
• Functions:
• strlen, strcmp, strpos, substr, as in C
• chop – remove whitespace from the right end
• trim – remove whitespace from both ends
• ltrim – remove whitespace from the left end
• strtolower, strtoupper
21

String functions
Function Parameter Returns
strlen A string The no. of characters in the string
strcmp Two strings 0, negative, or positive number
strpos Two strings The character position...
substr
A string and
an integer
The substring of the string, starting from
the second parameter (possibly, third
parameter for length)
chop A string Remove all whitespace from its end
trim A string Remove all whitespace from both ends
ltrim A string Remove all whitespace from its begin
strtolower A string All uppercase letters converted to
lowercase
strtoupper A string All lowercase letters converted to
uppercase
22

Example
$str = “Apples are good”;
$sub = substr ($str, 7, 1);
The value of $sub is „a‟.
23

Scalar Type Conversions
• Implicit type conversions (coercions)
• The context of an expression determines the type that is
expected or required
• When a numeric value appears in string context, the
numeric value is coerced to a string
• When a string value appears in numeric context, the
string value is coerced to a number.
• String to numeric
• If the string contains an e or an E, it is converted to
double; otherwise to integer
• If the string does not begin with a sign or a digit, the
conversion fails and zero is used
• Nonnumeric characters following the number in the
string are ignored.
24

Scalar Type Conversions
• Explicit type conversions in three different ways
• Using cast: (type_name) exp
(Ex) $total = 4.333; (int) $total // 4
• Using function: intval, doubleval, strval
(Ex) $total = 4.333; intval($total) // 4
• Using settype function: settype (variable, type_name)
(Ex) settype($total, "integer") // 4
• The type of a variable can be determined with gettype
or type testing functions
• gettype($total) - returns the type of the current value.
It may return "unknown"
• is_integer($total), is_float(), is_bool(), is_string()
– a predicate function
25

Output
• Any output from a PHP script becomes part of the
document the PHP processor is building
• An output from a PHP script is in the form of XHTML
that is sent to the browser
• XHTML is sent to the browser through standard output
• There are three ways to produce output :
• echo
• print
• printf
26

Output
• echo function
• If parentheses are included, only a single string parameter
is acceptable
• Otherwise, any number of parameters are acceptable
(Ex) echo "whatever", "it may ";
echo ("first ") ;
• returns no value
• echo and print take a string, but coerce other values
to strings
(Ex) echo 47 or print(47) will produce 47
27

Output
• print function:
• Called with only one parameter, possibly in a parenthesis
(Ex) print "Welcome to my site!";
• Will coerce non-string type value to a string
• Return a value (1 if successful, 0 otherwise)
• printf function
• Is like its counterpart in C
• Can control the format of displayed data completely
(Ex) $day = “Tuesday”;
$high = 79;
printf (“The high on %7s was %3d”, $day, $high);
28

Example
today.php
Welcome to my home page
Today is: Saturday, June 1st
29

Control Statements
• Relational Operators
• Use eight relational operators of JavaScript
• > , < , >= ,

Control Statements
• Selection statements
• if, if-else, elseif
• switch - as in C
• while - just like C
• do-while - just like C
• for - just like C
• foreach - discussed later
• break - in any for, foreach, while, do-while, or switch
• continue - in any loop
31

Alternative compound delimiters
• Applicable to if, switch, for, and while control
statements
• Opening delimiter is the colon with its own closing
reserved word
• More readable.
while ($a < 100) {
$a = $a * $b + 7;
$b++;
}
while ($a < 100) :
$a = $a * $b + 7;
$b++;
endwhile;
SHOW powers.html
32

Example
if ($day ==== “Saturday” || $day == “Sunday”)
$today = “weekend”;
else {
$today = “weekday”;
$work = true;
}
switch ($bordersize) {
case “0”: print “”; break;
case “1”: print “”; break;
case “4”: print “”; break;
case “8”: print “”; break;
default: print “Error-invalid value: $bordersize ”;
}
33

Example
$fact = 1;
$count = 1;
while ($count < $n) {
$count ++;
$fact *= $count;
}
for ($count = 1, $fact = 1; $count < $n) {
$count++;
$fact *= $count;
}
34

HTML/PHP document
• HTML can be intermingled with PHP script
35

Example
powers.php
Powers table
Number
Square Root
Square
Cube
Quad
36

Result
Powers table
Number Square Root Square Cube Quad
1 1 1 1 1
2 1.4142125623731 4 8 16
3 1.7320508075689 9 27 81
4 2 16 64 256
5
6
7
8
9
10
38

PHP in HTML
• HTML
PHP
Programming
• PHP in HTML
39

PHP in HTML
• Using variable
40