PHP = Personal Home Page - uml.eduhaim/teaching/iws/513/resources/presentations/12... · Array...

1© Copyright 2006-2007 Haim Levkowitz

PHP = Personal Home Page

• Or PHP: Hypertext Preprocessor


Origins and Uses

• Origins• Rasmus Lerdorf - 1994• Developed to track visitors to his Web

site• open-source product• PHP = Personal Home Page• Or PHP: Hypertext Preprocessor

• Used for form handling, file processing,database access


PHP Overview

• Server-side scripting language• scripts embedded in HTML documents• Similar to JavaScript, but on server side

• Alternative to CGI, ASP.NET, JSP, Allaire’sColdFusion

• PHP processor has two modes:• copy (XHTML)• interpret (PHP)


PHP Overview (cont.)

• Syntax similar to JavaScript

• Dynamically typed

• Purely interpreted


General SyntacticCharacteristics• PHP code can be specified in XHTML document

• internally or externally:• Internally:

• <?php• ...• ?>

• Externally: include ("myScript.inc")• file can have both PHP and XHTML• If file has PHP, must be in

• <?php .. ?>• even if include already in <?php .. ?>

• Every variable name begin with $


General SyntacticCharacteristics (cont.)

• Comments• three different kinds (Java and Perl)• // ...• # ...• /* ... */

• Compound statements• formed with braces• cannot be blocks


Primitives, Operations,Expressions

• Variables• no type declarations• unassigned (unbound) variable has valueNULL• unset function sets variable to NULL• IsSet function used to determine

whether variable is NULL


Primitives, Operations,Expressions (cont.)

• error_reporting(15);• prevents PHP from using unbound

variables• many predefined variables,• including environment variables of host

OS• can get list of predefined variables by

calling phpinfo() in script


Eight primitive types

• Four scalar types• Boolean, integer, double, and string

• Two compound types• array and object

• Two special types:• resource and NULL

• Integer & double• like those of other languages

• Strings• Characters are single bytes• String literals use single or double quotes


Primitives, Operations,Expressions (cont.)

• Single-quoted string literals• (as in Perl)• Embedded variables NOT

interpolated• Embedded escape sequences NOT

recognized


• Double-quoted string literals (as in Perl)• Embedded variables ARE interpolated• If there is variable name in double-quoted string

• but don’t want it interpolated,• must be backslashed

• Embedded escape sequences ARE recognized• For both single- and double-quoted literal strings,

embedded delimiters must be backslashed• Boolean-values are true and false (case insensitive)

• 0 and "" and "0" are false• others are true


Primitives, Operations,Expressions (cont.)• Arithmetic Operators and Expressions• Usual operators

• If result of integer division not integer• double returned

• Any integer operation that results in overflow• produces double

• Modulus operator coerces its operands tointeger, if necessary

• When double is rounded to integer• rounding always towards zero


Arithmetic functions

• floor• ceil• round• abs• min• max• rand• etc.


String Operations andFunctions

• only operator• period• concatenation

• Indexing• $str{3}= fourth character


String Operations andFunctions (cont.)• Functions:

• strlen, strcmp, strpos, substr• as in C

• chop• remove whitespace from right end

• trim• remove whitespace from both ends

• ltrim• remove whitespace from left end

• strtolower, strtoupper


Scalar type conversions:String to numeric

• If string• contains e or E• converted to double

• otherwise• to integer

• does not begin with sign or digit• zero is used


Scalar type conversions(cont.)

• Explicit conversions – casts• e.g.,• (int)$total• or• settype($total, "integer")


Determine type ofvariable

• gettype or is_type• gettype($total)• may return "unknown"

• is_integer($total)• predicate function


Output

• HTML

• Sent to browser

• Through standard output


Three ways to produceoutput

• echo, print, printf• echo and print

• take string• but will coerce other values to strings

• echo "whatever"; # Only one parameter• echo("first ", $sum) # More thanone

• print "Welcome to my site!"; # Only one


PHP code place in body ofXHTML doc• <html>

• <head>• <title> Trivial php example </title>• </head>• <body>• <?php• print "Welcome to my Web site!";• ?>• </body>

• </html>• -> SHOW today.php and display


Control statements

• Control Expressions• Relational operators• same as JavaScript• including === and !==

• Boolean operators• same as Perl• two sets, && and and, etc.


Selection statements

• if, if-else, elseif• switch

• as in C• switch expression type must be integer,

double, or string• while, do-while, for

• just like C• foreach

• later


Control statements(cont.)• break

• in any for, foreach, while, do-while, or switch• continue

• in any loop• Alternative compound delimiters

• more readability• if(...):

• ...• endif;

• SHOW powers.php


Can intermingle HTML, PHP

<?php $a = 7; $b = 7; if ($a == $b) { $a = 3 * $a; ?> At this point, $a and $b are equal So, we change $a to three times $a <?php }

?>


Arrays

• Not like arrays of other programming language• generalization• mapping of keys to values• keys can be

• numbers• traditional array

• strings• hash (“associative array”)


Array creation

• Use array() construct• takes one or more key => value pairs as parameters• returns array of them• keys

• non-negative integer literals, or• string literals

• values can be anything• e.g.,

• $list = array(0 => "apples", 1 =>"oranges", 2 => "grapes")

• “regular” array of strings


Arrays (cont.)

• If key is omitted, and• there have been integer keys• default key will be largest current key + 1

• there have been no integer keys• 0 is default key

• If key appears that has already appeared• new value will overwrite old one


Arrays can have mixedkinds of elements• e.g.,• $list = array("make" => "Cessna",• "model" => "C210",• "year" => 1960,• 3 => "sold");

• $list = array(1, 3, 5, 7, 9);

• $list = array(5, 3 => 7, 5 => 10,• "month" => "May");

• $colors = array('red', 'blue', 'green',• 'yellow');


Accessing array elements –use brackets• $list[4] = 7;• $list["day"] = "Tuesday";• $list[] = 17;• If element with specified key does not exist

• element is created• If array does not exist

• array is created


Extract keys, values fromarray

• $highs = array("Mon" => 74,"Tue" => 70,"Wed" => 67,"Thu" => 62,"Fri" => 65);

• $days = array_keys($highs);• $temps = array_values($highs);


Dealing with Arrays

• Array can be deleted with unset• unset($list);• unset($list[4]); # No index4 element now


• is_array($list)• returns true if $list is array

• in_array(17, $list)• returns true if 17 is an element of $list

• explode(" ", $str)• creates array with values of words from $str• split on space

• implode(" ", $list)• creates string of elements from $list• separated by space


Sequential access to arrayelements

• current and next• $colors = array("Blue", "red", "green",• "yellow");• $color = current($colors);• print("$color ");• while ($color = next($colors))• print ("$color ");


• This does not always work• E.g, when value in array = FALSE

• Alternative: each, instead of next• while ($element = each($colors)) { print ("$element['value'] ");

• prev function• moves current backwards

• array_push($list, $element) and• array_pop($list)


Implement stacks witharrays

• foreach (array_name as scalar_name) { ... }

• foreach ($colors as $color) {• print• "Is $color your favorite color? ";• }

• Is red your favorite color?• Is blue your favorite color?• Is green your favorite color?• Is yellow your favorite color?


• foreach can iterate through both keys andvalues:

• foreach ($colors as $key => $color) { … }• Inside compound statement

• both $key and $color are defined• $ages = array("Bob" => 42, "Mary" => 43);• foreach ($ages as $name => $age)• print("$name is $age years old ");


sort

• sort values of array• leave keys in their present order• intended for traditional arrays• e.g.,• sort($list);

• sort function does not return anything• Works for both strings and numbers• even mixed strings and numbers


• $list = ('h', 100, 'c', 20, 'a');• sort($list);• // Produces ('a', 'c', 'h‘, 20, 100)

• In PHP 4, sort function can take second parameter• specifies particular kind of sort• sort($list, SORT_NUMERIC);

• asort• sort values of array• but keep key/value relationships

• intended for hashes


• rsort

• sort values of array into reverse order• ksort

• sort elements of array by keys

• maintain key/value relationships

• e.g., …


• $list("Fred" => 17, "Mary" => 21,• "Bob" => 49, "Jill" => 28);• ksort($list);• // $list is now ("Bob" => 49,• // "Fred" => 17, "Jill" => 28, "Mary" => 21)• krsort

• sort elements of array by keys into reverse order• SHOW sorting.php


User-Defined Functions

• Syntactic form:• function

function_name(formal_parameters){

…}


General Characteristics

• Functions need not be defined beforethey are called

• (in PHP 3, they must)• Function overloading not supported

• If try to redefine function

• error


• Functions can have variable number ofparameters

• Default parameter values supported• Function definitions can be nested• Function names NOT case sensitive• return function used to return value• If there is no return• no returned value


Parameters

• If caller sends too many actual parameters• subprogram ignores extra ones

• If caller does not send enough parameters• unmatched formal parameters

unbound• default parameter passing method• pass by value• (one-way communication)


To specify pass-by-reference

• prepend ampersand to formalparameter

• function addOne(&$param) {$param++;

}

$it = 16;addOne($it); // $it is now 17


If function does not specifyparameter to be pass byreference• can prepend ampersand to actual parameter

and still get pass-by-reference semantics

• function subOne($param) { $param--; }$it = 16;subOne(&$it); // $it is now 15


Return Values

• Any type may be returned• including objects and arrays• using return

• If function returns reference• name of function must have prepended

ampersand

• function &newArray($x) { … }


Scope of Variables

• undeclared variable in function

• has scope of function

• To access a nonlocal variable• it must be declared to be global’

• as in• global $sum;


Lifetime of Variables

• Normally

• from first appearance

• to end of function’s execution• static $sum = 0; # $sum isstatic


Pattern Matching

• two kinds:

• POSIX

• Perl-compatible• preg_match(regex, str [,array])• optional array

• where to put matches


Form Handling

• Simpler with PHP than

• CGI or servlets

• Forms could be handled by samedocument that creates the form

• but that may be confusing


PHP particulars:

• It does not matter whether GET or POST methodused to transmit form data

• PHP builds array of the form values• $_GET for GET method and• $_POST for POST method• subscripts are widget names

• SHOW popcorn3.html• SHOW popcorn3.php


Files

• PHP can:• Deal with any files on• server• Internet

• using either• http or ftp

• Instead of filehandles• PHP associates variable with file• called file variable

• (for program reference)


• file has file pointer (where to read or write)• $fptr = fopen(filename, use_indicator)

• Use indicators:• r read only, from beginning• r+ read and write, from beginning• w write only, from beginning• (also creates file, if necessary)• w+ read and write, from beginning• (also creates file, if necessary)• a write only, at end, if exists• (creates file, if necessary)• a+ read and write, read at beginning, write• at end

• Because fopen could fail, use with die• Use file_exists(filename) to determine whether file exists

before trying to open it• Use fclose(file_var) to close file


Reading files

• 1. Read all or part of file into stringvariable

• $str = fread(file_var, #bytes)• To read whole file, use• filesize(file_name)• as second parameter


Reading files

• 2. Read lines of file into array• @file_lines = file(file_name)• Need not open or close file


Reading files

• 3. Read one line from file• $line = fgets(file_var, #bytes)• Reads characters until• eoln• eof• Or #bytes characters have been

read


Reading files

• 4. Read one character at a time• $ch = fgetc(file_var)• Control reading lines or characters with

eof detection using feof• TRUE for eof; FALSE otherwise

• while(!feof($file_var)) {$ch = fgetc($file_var);

}


Writing to files

• $bytes_written = fwrite(file_var,string)

• fwrite returns number of bytes it wrote• Files can be locked• avoid interference from concurrent

accesses• with flock• just like Perl


Cookies

• Create cookie with setcookie• setcookie(cookie_name,

cookie_value, lifetime)

• e.g.,


e.g.,

• setcookie("voted", "true", time() +86400);

• Cookies• must be created before any other

HTML created by script• obtained in script same way form

values gotten• using the $_COOKIES array


Session tracking

• PHP creates and maintains session tracking id• Create id with call to

• session_start• with no parameters

• Subsequent calls to session_start• retrieve any session variables• previously registered in session


To create session variable

• Use session_register

• only parameter is string literal ofname of session variable• without dollar sign


Example

• count number of pages visited• Put following code in all documents• session_start();if (!IsSet($page_number))$page_number = 1;print("You have now visited$page_number");print(" pages ");$page_number++;$session_register("page_number");

Date post:	26-Mar-2018
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