Php introduction

PHP Krishna priya April 19, 2011 C-DAC, Hyderabad

What is PHP? PHP == ‘Hypertext Preprocessor’ Open-source, server-side scripting language Used to generate dynamic web-pages PHP scripts reside between reserved PHP tags This allows the programmer to embed PHP scripts within HTML pages

What is PHP (cont’d) Interpreted language, scripts are parsed at runtime rather than compiled beforehand Executed on the server-side Source-code not visible by client ‘View Source’ in browsers does not display the PHP code Various built-in functions allow for fast development Compatible with many popular databases including MySQL, PostgreSQL, Oracle, Sybase, Informix, and Microsoft SQL Server.

Brief History of PHP PHP (PHP: Hypertext Preprocessor) was created by Rasmus Lerdorf in 1994. It was initially developed for HTTP usage logging and serverside form generation in Unix. PHP 2 (1995) transformed the language into a Server-side embedded scripting language. Added database support, file uploads, variables, arrays, recursive functions, conditionals, iteration, regular expressions, etc. PHP 3 (1998) added support for ODBC(Open Database Connectivity) data sources, multiple platform support, email protocols and new parser written

Brief History of PHP (cont’d) PHP 4 (2000) became an independent component of the web server for added efficiency. The parser was renamed the Zend Engine. Many security features were added. PHP 5 (2004) adds Zend Engine II with object oriented programming, robust XML support, SOAP extension for interoperability with Web Services, SQLite(SQLite is an embedded database library that implements a large subset of the SQL 92 standard.) has been bundled with PHP

Advantages of selecting PHP for Web Development 1. It can be easily embedded into the HTML code. 2. There is no need to pay for using PHP to develop web applications and websites. 3. It provides support to almost all operating systems that include Windows, Linux, Mac, etc. 4. Implementing PHP is much easier than other programming languages like Java, Asp.net, C++, etc. 5. PHP provides compatibility to all web browsers. Be it Internet Explorer, Mozilla Firefox, Netscape, Google Chrome, Opera, or any other Web browser, PHP supports all. 6. PHP is compatible with web servers like Apache, IIS, etc. 7. PHP Web development is highly reliable and secure because of the security features that PHP offers. 8. Provides support to all database servers, such as MSSQL, Oracle, and MySQL. Because it provides supports for almost all database servers, it is highly used in developing dynamic web applications. 9. It is the best choice to develop small as well as large websites like ecommerce websites, discussion forums, etc. 10. It offers flexibility, scalability, and faster speed in comparison to other scripting languages being used to develop websites.

PHP Environment Setup In order to develop and run PHP Web pages three vital components need to be installed on your computer system. Web Server, Database , PHP Parser Wamp Server is an open source project http://www.wampserver.com/en/dow nload.php Wamp Server Version 2.0 PHP:5.2.5, Apache:2.2.6, MYSQL:5.0.45

How PHP works When a user navigates in his/her browser to a page that ends with a .php extension, the request is sent to a web server, which directs the request to the PHP interpreter.

What does PHP code look like? Structurally similar to C/C++ Here some similarities and differences in PHP and C: Similarities: Broadly speaking, PHP syntax is the same as in C: statements are terminated with semicolons, function calls have the same structure (my_function(expression1, expression2)), and curly braces ({ and }) make statements into blocks. PHP supports C and C++-style comments (/* */ as well as //), and also Perl and shell-script style (#).

Similarities(cont’d) Operators: The assignment operators (=, +=, *=, and so on), Boolean operators (&&, ||, !) the comparison operators (<,>, <=, >=, ==, !=), and the basic arithmetic operators (+, -, *, /, %) all behave in PHP as they do in C. Control structures: The basic control structures (if, switch, while, for) behave as they do in C, including supporting break and continue. One notable difference is that switch in PHP can accept strings as case identifiers.

Similarities (cont’d) Function names: As you peruse the documentation, you all see many function names that seem identical to C functions. Differences: Dollar signs: All variables are denoted with a leading $. Variables do not need to be declared in advance of assignment

Differences compare to C Types: PHP has only two numerical types: integer (corresponding to a long in C) and double (corresponding to a double in C). Strings are of arbitrary length. There is no separate character type. Arrays: Arrays have a syntax superficially similar to C's array syntax, but they are implemented completely differently. They are actually associative arrays or hashes, and the index can be either a number or a string. They do not need to be declared or allocated in advance.

Differences compare to C No structure type: There is no struct in PHP No pointers: There are no pointers available in PHP. PHP does support variable references. You can also emulate function pointers to some extent, in that function names can be stored in variables and called by using the variable rather than a literal name.

Differences compare to C No prototypes: Functions do not need to be declared before their implementation is defined, as long as the function definition can be found somewhere in the current code file or included files.

PHP Language Basics Structurally similar to C/C++ All PHP statements end with a semi-colon Each PHP script must be enclosed in the reserved PHP tag PHP Tag Styles as follows: <?php … ?> short-open tag <?...?> ASP-style tags <%...%> HTML script tags <script language="PHP">...</script>

Comments in PHP There are two commenting formats in PHP: 1. Single-line comments 2. Multi-lines comments // C++ and Java-style comment # This is the second line of the comment /* C-style comments These can span multiple lines */

PHP Variables PHP variables must begin with a “$” sign Case-sensitive ($Foo != $foo != $fOo) Certain variable names reserved by PHP For Example Form variables ($_POST, $_GET) Etc. <?php $foo = 25; $bar = “Hello”; // Numerical variable // String variable $foo = ($foo * 7); // Multiplies foo by 7 ?>

PHP Variable Naming Conventions There are a few rules that you need to follow when choosing a name for your PHP variables. PHP variables must start with a letter or underscore "_". PHP variables may only be comprised of alpha-numeric characters and underscores. a-z, A-Z, 0-9, or _ . Variables with more than one word should be separated with underscores. $my_variable Variables with more than one word can also be distinguished with capitalization. $myVariable

Echo The PHP command ‘echo’ is used to output the parameters passed to it Strings in single quotes (‘ ’) are not interpreted or evaluated by PHP <?php $foo = 25; $bar = “Hello”; echo echo echo echo echo ?> // Numerical variable // String variable $bar; // Outputs Hello $foo,$bar; // Outputs 25Hello “5x5=”,$foo; // Outputs 5x5=25 “5x5=$foo”; // Outputs 5x5=25 ‘5x5=$foo’; // Outputs 5x5=$foo Notice how echo ‘5x5=$foo’ outputs $foo rather than replacing it with 25 Strings in single quotes (‘ ’) are not interpreted or evaluated by PHP

Concatenation Use a period to join strings into one. <?php $string1=“Hello”; $string2=“PHP”; $string3=$string1 . “ ” . $string2; echo $string3; ?> Hello PHP Escaping the Character If the string has a set of double quotation marks that must remain visible, use the [backslash] before the quotation marks to ignore and display them. <?php $heading=“”Computer Science””; Print $heading; ?> “Computer Science”

Operators Examples Assume variable A holds 10 and variable B holds 20 then: Type Operator Description Example Arithmetic + Adds two operands A + B will give 30 Comparision == Checks if the value of two operands are equal or not, if yes then condition becomes true. (A == B) is not true. Logical (or Relational) Operators and If both the operands are true then then condition becomes true. (A and B) is true. Assignment Operators += It adds right operand to the left operand and assign the result to left operand C += A is equivalent to C = C+A Conditional (or ternary) Operators ?: Conditional Expression If Condition is true ? Then value X : Otherwise value Y

PHP Decision Making The if, else …elseif and switch statements are used to take decision based on the different condition. <?php $my_name = "someguy"; if ( $my_name == "someguy" ) { echo "Your name is someguy!<br />"; } echo "Welcome to my homepage!"; ?> No THEN in PHP <?php If($user==“John”) { Print “Hello John.”; } Else { Print “You are not John.”; } ?>

PHP Loop Types Loops in PHP are used to execute the same block of code a specified number of times. PHP supports following four loop types. While while - loops through a block of code if and as long as a specified condition is true. do...while do...while - loops through a block of code once, and then repeats the loop as long as a special condition is true. for – loop for - loops through a block of code a specified number of times. foreach foreach - loops through a block of code for each element in an array.

PHP Arrays An array stores one or more similar type of values in a single value. An array is a special variable, which can store multiple values in one single variable. In PHP, there are three kind of arrays: Numeric array - An array with a numeric index Associative array - An array where each ID key is associated with a value Multidimensional array - An array containing one or more arrays

Looping through Arrays Looping through element values Looping through keys and values foreach ( $array as $value ) { // Do stuff with $value } foreach ( $array as $key => $value ) { // Do stuff with $key and/or $value } Sorting an Array in PHP You can sort an array in PHP by using two functions: sort(), to sort an array in ascending order rsort(), to sort an array in the reverse order, or descending order

Date Display $datedisplay=date(“yyyy/m/d”); echo $datedisplay; 2011/4/19 Tuesday, April 19, 2011 Tue $datedisplay=date(“l, F m, Y”); echo $datedisplay; $date display=date(“D”); echo $d

Functions PHP functions are similar to other programming languages. A function is a piece of code which takes one more input in the form of parameter and does some processing and returns a value. There are two parts which should be clear to you: Creating a PHP Function Calling a PHP Function function functionName() { code to be executed; }

PHP File Inclusion You can include the content of a PHP file into another PHP file before the server executes it. There are two PHP functions which can be used to included one PHP file into another PHP file. The include() Function The require() Function This is a strong point of PHP which helps in creating functions, headers, footers, or elements that can be reused on multiple pages. This will help developers to make it easy to change the layout of complete website with minimal effort. If there is any change required then instead of changing thausand of files just change included file.

Php introduction

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