Bài giảng Web Technologies and e-Services - Bài 5, Phần 1: PHP

PHP 1 Content 2 PHP Basics: ▪ Introduction to PHP • a PHP file, PHP workings, running PHP. ▪ Basic PHP syntax • variables, operators, if...else...and switch, while, do while, and for. ▪ Some useful PHP functions ▪ How to work with • HTML forms, cookies, files, time and date. ▪ How to create a basic checker for user-entered data Introduction to PHP • Server-side programming tries to avoid the drawbacks ▪ Code is embedded in HTML pages, and evaluated on the server while the pages are being served. Add dynamically generated content to an existing HTML page. • Active Server Pages (ASP, Microsoft) : The ASP engine is integrated into the web server so it does not require an additional process. It allows programmers to mix code within HTML pages instead of writing separate programs. (Drawback(?) Must be run on a server using Microsoft server software.) • Java Servlets (Sun): As CGI scripts, they are code that creates documents. These must be compiled as classes which are dynamically loaded by the web server when they are run. • Java Server Pages (JSP): Like ASP, another technology that allows developers to embed Java in web pages. 3 Introduction to PHP • Developed in 1995 by Rasmus Lerdorf (member of the Apache Group) ▪ originally designed as a tool for tracking visitors at Lerdorf's Web site ▪ within 2 years, widely used in conjunction with the Apache server ▪ free, open-source ▪ now fully integrated to work with mySQL databases • PHP is similar to JavaScript, only it’s a server-side language ▪ PHP code is embedded in HTML using tags ▪ when a page request arrives, the server recognizes PHP content via the file extension (.php or .phtml) ▪ the server executes the PHP code, substitutes output into the HTML page ▪ the resulting page is then downloaded to the client ▪ user never sees the PHP code, only the output in the page • The acronym PHP means (in a slightly recursive definition) ▪ PHP: Hypertext Preprocessor 4 Basic PHP syntax A PHP scripting block always starts with <?php and ends with ?>. A PHP scripting block can be placed (almost) anywhere in an HTML document. Hello World This is going to be ignored by the PHP interpreter. While this is going to be parsed.'; ?> This will also be ignored by the PHP preprocessor. Hello and welcome to my page!'); ?> <?php //This is a comment /* This is a comment block */ ?> The server executes the print and echo statements, substitutes output. print and echo for output a semicolon (;) at the end of each statement view the output page // for a single-line comment /* and */ for a large comment block. Scalars All variables in PHP start with a $ sign symbol. A variable's type is determined by the context in which that variable is used (i.e. there is no strong-typing in PHP). <?php $foo = true; if ($foo) echo "It is TRUE! \n"; $txt='1234'; echo "$txt \n"; $a = 1234; echo "$a \n"; $a = -123; echo "$a \n"; $a = 1.234; echo "$a \n"; $a = 1.2e3; echo "$a \n"; $a = 7E-10; echo "$a \n"; echo 'Arnold once said: "I\'ll be back"', " \n"; $beer = 'Heineken'; echo "$beer's taste is great \n"; $str = <<<EOD Example of string spanning multiple lines using “heredoc” syntax. EOD; echo $str; ?> Four scalar types: boolean true or false integer, float, floating point numbers string single quoted double quotedview the output page Arrays array() = creates arrays<?php $arr = array("foo" => "bar", 12 => true); echo $arr["foo"]; // bar echo $arr[12]; // 1 ?> key = either an integer or a string. value = any PHP type. <?php array(5 => 43, 32, 56, "b" => 12); array(5 => 43, 6 => 32, 7 => 56, "b" => 12); ?> if no key given (as in example), the PHP interpreter uses (maximum of the integer indices + 1). if an existing key, its value will be overwritten. <?php $arr = array(5 => 1, 12 => 2); foreach ($arr as $key => $value) { echo $key, '=>', $value); } $arr[] = 56; // the same as $arr[13] = 56; $arr["x"] = 42; // adds a new element unset($arr[5]); // removes the element unset($arr); // deletes the whole array $a = array(1 => 'one', 2 => 'two', 3 => 'three'); unset($a[2]); $b = array_values($a); ?> can set values in an array unset() removes a key/value pair *Find more on arrays array_values() makes reindexing effect (indexing numerically) view the output page Constants A constant is an identifier (name) for a simple value. A constant is case-sensitive by default. By convention, constant identifiers are always uppercase. <?php // Valid constant names define("FOO", "something"); define("FOO2", "something else"); define("FOO_BAR", "something more"); // Invalid constant names (they shouldn’t start // with a number!) define("2FOO", "something"); // This is valid, but should be avoided: // PHP may one day provide a "magical" constant // that will break your script define("__FOO__", "something"); ?> You can access constants anywhere in your script without regard to scope. Operators • Arithmetic Operators: +, -, *,/ , %, ++, -- • Assignment Operators: =, +=, -=, *=, /=, %= • Comparison Operators: ==, !=, >, =, <= • Logical Operators: &&, ||, ! • String Operators: . and .= (for string concatenation) Example Is the same as x+=y x=x+y x-=y x=x-y x*=y x=x*y x/=y x=x/y x%=y x=x%y $a = "Hello "; $b = $a . "World!"; // now $b contains "Hello World!" $a = "Hello "; $a .= "World!"; Conditionals: if else Can execute a set of code depending on a condition <?php $d=date("D"); echo $d, ""; if ($d=="Fri") echo "Have a nice weekend! "; else echo "Have a nice day! "; $x=10; if ($x==10) { echo "Hello"; echo "Good morning"; } ?> if (condition) code to be executed if condition is true; else code to be executed if condition is false; view the output page date() is a built-in PHP function that can be called with many different parameters to return the date (and/or local time) in various formats In this case we get a three letter string for the day of the week. Conditionals: switch Can select one of many sets of lines to execute <?php $x = rand(1,5); // random integer echo "x = $x "; switch ($x) { case 1: echo "Number 1"; break; case 2: echo "Number 2"; break; case 3: echo "Number 3"; break; default: echo "No number between 1 and 3"; break; } ?> 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; break; } view the output page Looping: while and do-while Can loop depending on a condition <?php $i=1; while($i <= 5) { echo "The number is $i "; $i++; } ?> loops through a block of code if, and as long as, a specified condition is true view the output page <?php $i=0; do { $i++; echo "The number is $i "; } while($i <= 10); ?> loops through a block of code once, and then repeats the loop as long as a special condition is true (so will always execute at least once) view the output page Looping: for and foreach Can loop depending on a "counter" <?php for ($i=1; $i<=5; $i++) { echo "Hello World!"; } ?> loops through a block of code a specified number of times <?php $a_array = array(1, 2, 3, 4); foreach ($a_array as $value) { $value = $value * 2; echo "$value \n"; } ?> loops through a block of code for each element in an array <?php $a_array=array("a","b","c"); foreach ($a_array as $key => $value) { echo $key . " = " . $value . "\n"; } ?>view the output page User Defined Functions Can define a function using syntax such as the following: <?php function foo($arg_1, $arg_2, /* ..., */ $arg_n) { echo "Example function.\n"; return $retval; } ?> Can also define conditional functions, functions within functions, and recursive functions. <?php function square($num) { return $num * $num; } echo square(4); ?> <?php function small_numbers() { return array (0, 1, 2); } list ($zero, $one, $two) = small_numbers(); echo $zero, $one, $two; ?> Can return a value of any type <?php function takes_array($input) { echo "$input[0] + $input[1] = ", $input[0]+$input[1]; } takes_array(array(1,2)); ?> view the output page Variable Scope The scope of a variable is the context within which it is defined. <?php $a = 1; /* limited variable scope */ function Test() { echo $a; /* reference to local scope variable */ } Test(); ?> The scope is local within functions, and hence the value of $a is undefined in the “echo” statement. <?php $a = 1; $b = 2; function Sum() { global $a, $b; $b = $a + $b; } Sum(); echo $b; ?> global refers to its global version. <?php function Test() { static $a = 0; echo $a; $a++; } Test1(); Test1(); Test1(); ?> static does not lose its value. view the output page Including Files The include() statement includes and evaluates the specified file. // vars.php <?php $color = 'green'; $fruit = 'apple'; ?> // test.php <?php echo "A $color $fruit"; // A include 'vars.php'; echo "A $color $fruit"; // A green apple ?> *The scope of variables in “included” files depends on where the “include” file is added! You can use the include_once, require, and require_once statements in similar ways. view the output page <?php function foo() { global $color; include ('vars.php‘); echo "A $color $fruit"; } /* vars.php is in the scope of foo() so * * $fruit is NOT available outside of this * * scope. $color is because we declared it * * as global. */ foo(); // A green apple echo "A $color $fruit"; // A green ?> view the output page PHP Information The phpinfo() function is used to output PHP information about the version installed on the server, parameters selected when installed, etc. <!– info.php CS443 <?php // Show all PHP information phpinfo(); ?> <?php // Show only the general information phpinfo(INFO_GENERAL); ?> INFO_GENERAL The configuration line, php.ini location, build date, Web Server, System and more INFO_CREDITS PHP 4 credits INFO_CONFIGURATION Local and master values for php directives INFO_MODULES Loaded modules INFO_ENVIRONMENT Environment variable information INFO_VARIABLES All predefined variables from EGPCS INFO_LICENSE PHP license information INFO_ALL Shows all of the above (default) view the output page Server Variables The $_SERVER array variable is a reserved variable that contains all server information. <?php echo "Referer: " . $_SERVER["HTTP_REFERER"] . ""; echo "Browser: " . $_SERVER["HTTP_USER_AGENT"] . ""; echo "User's IP address: " . $_SERVER["REMOTE_ADDR"]; ?> <?php echo ""; echo "All information"; foreach ($_SERVER as $key => $value) { echo $key . " = " . $value . ""; } ?> The $_SERVER is a super global variable, i.e. it's available in all scopes of a PHP script. view the output page $_SERVER info on php.net File Open The fopen("file_name","mode") function is used to open files in PHP. <?php $fh=fopen("welcome.txt","r"); ?> r Read only. r+ Read/Write. w Write only. w+ Read/Write. a Append. a+ Read/Append. x Create and open for write only. x+ Create and open for read/write. If the fopen() function is unable to open the specified file, it returns 0 (false). <?php if ( !($fh=fopen("welcome.txt","r")) ) exit("Unable to open file!"); ?> For w, and a, if no file exists, it tries to create it (use with caution, i.e. check that this is the case, otherwise you’ll overwrite an existing file). For x if a file exists, this function fails (and returns 0). File Workings fclose() closes a file. feof() determines if the end is true. fgetc() reads a single character <?php $myFile = "welcome.txt"; if (!($fh=fopen($myFile,'r'))) exit("Unable to open file."); while (!feof($fh)) { $x=fgetc($fh); echo $x; } fclose($fh); ?> <?php $myFile = "welcome.txt"; $fh = fopen($myFile, 'r'); $theData = fgets($fh); fclose($fh); echo $theData; ?> fgets() reads a line of data fwrite(), fputs () writes a string with and without \n <?php $myFile = "testFile.txt"; $fh = fopen($myFile, 'a') or die("can't open file"); $stringData = "New Stuff 1\n"; fwrite($fh, $stringData); $stringData = "New Stuff 2\n"; fwrite($fh, $stringData); fclose($fh); ?> file() reads entire file into an array <?php $lines = file('welcome.txt'); foreach ($lines as $l_num => $line) { echo "Line #{$l_num}:“ .$line.””; } ?> view the output page view the output page view the output page view the output page Form Handling Any form element is automatically available via one of the built-in PHP variables (provided that HTML element has a “name” defined with it). Enter your name: Enter your age: Welcome You are years old! $_POST contains all POST data. $_GET contains all GET data. view the output page Cookie Workings setcookie(name,value,expire,path,domain) creates cookies. <?php setcookie("uname", $_POST["name"], time()+36000); ?> Dear , a cookie was set on this page! The cookie will be active when the client has sent the cookie back to the server. NOTE: setcookie() must appear BEFORE (or any output) as it’s part of the header information sent with the page. view the output page <?php if ( isset($_COOKIE["uname"]) ) echo "Welcome " . $_COOKIE["uname"] . "!"; else echo "You are not logged in!"; ?> use the cookie name as a variable isset() finds out if a cookie is set $_COOKIE contains all COOKIE data. view the output page Getting Time and Date date() and time () formats a time or a date. <?php //Prints something like: Monday echo date("l"); //Like: Monday 15th of January 2003 05:51:38 AM echo date("l jS \of F Y h:i:s A"); //Like: Monday the 15th echo date("l \\t\h\e jS"); ?> date() returns a string formatted according to the specified format. <?php $nextWeek = time() + (7 * 24 * 60 * 60); // 7 days; 24 hours; 60 mins; 60secs echo 'Now: '. date('Y-m-d') ."\n"; echo 'Next Week: '. date('Y-m-d', $nextWeek) ."\n"; ?> time() returns current Unix timestamp view the output page view the output page Required Fields in User-Entered Data A multipurpose script which asks users for some basic contact information and then checks to see that the required fields have been entered. PHP Form example <?php /*declare some functions*/ function print_form($f_name, $l_name, $email, $os) { ?> First Name: " /> Last Name *:" /> Email Address *:" /> Operating System: " /> <?php } //** end of "print_form" function Print Function Check and Confirm Functions function check_form($f_name, $l_name, $email, $os) { if (!$l_name||!$email){ echo "You are missing some required fields!"; print_form($f_name, $l_name, $email, $os); } else{ confirm_form($f_name, $l_name, $email, $os); } } //** end of "check_form" function function confirm_form($f_name, $l_name, $email, $os) { ?> Thanks! Below is the information you have sent to us. Contact Info <?php echo "Name: $f_name $l_name "; echo "Email: $email "; echo "OS: $os"; } //** end of "confirm_form" function Main Program /*Main Program*/ if (!$_POST["submit"]) { ?> Please enter your information Fields with a "*" are required. <?php print_form("","","",""); } else{ check_form($_POST["f_name"],$_POST["l_name"],$_POST["email"],$_POST["os"]); } ?> view the output page Learning Outcomes In the lecture you have learned ▪ What is PHP and what are some of its workings. ▪ Basic PHP syntax • variables, operators, if...else...and switch, while, do while, and for. ▪ Some useful PHP functions ▪ How to work with • HTML forms, cookies, files, time and date. ▪ How to create a basic checker for user-entered data. 28