PHP Study Material PDF

PHP Study Material 4.1 Introduction to PHP & Features 4.2 PHP Scripts 4.3 Data Types 4.4 Variables 4.5 Operators 4.6 Control Structures 4.7 Working with Arrays 4.8 Functions 4.9 Working with Files 4.10 Working with Databases 4.1 Introduction to PHP & Features PHP is a...

PHP Study Material 4.1 Introduction to PHP & Features 4.2 PHP Scripts 4.3 Data Types 4.4 Variables 4.5 Operators 4.6 Control Structures 4.7 Working with Arrays 4.8 Functions 4.9 Working with Files 4.10 Working with Databases 4.1 Introduction to PHP & Features PHP is a server scripting language, and a powerful tool for making dynamic and interactive Web pages. PHP is a widely-used, free, and efficient alternative to competitors such as Microsoft's ASP. Example What You Should Already Know Before you continue you should have a basic understanding of the following: HTML CSS JavaScript What is PHP?  PHP is an acronym for "PHP: Hypertext Preprocessor" PHP is a widely-used, open source scripting language PHP scripts are executed on the server PHP is free to download and use What is a PHP File? PHP files can contain text, HTML, CSS, JavaScript, and PHP code PHP code are executed on the server, and the result is returned to the browser as plain HTML PHP files have extension ".php" What Can PHP Do? PHP can generate dynamic page content PHP can create, open, read, write, delete, and close files on the server PHP can collect form data PHP can send and receive cookies PHP can add, delete, modify data in your database PHP can be used to control user-access PHP can encrypt data With PHP you are not limited to output HTML. You can output images, PDF files, and even Flash movies. You can also output any text, such as XHTML and XML. Why PHP? PHP runs on various platforms (Windows, Linux, Unix, Mac OS X, etc.) PHP is compatible with almost all servers used today (Apache, IIS, etc.) PHP supports a wide range of databases PHP is free. Download it from the official PHP resource: www.php.net PHP is easy to learn and runs efficiently on the server side To start using PHP, you can: Find a web host with PHP and MySQL support Install a web server on your own PC, and then install PHP and MySQL Use a Web Host with PHP Support If your server has activated support for PHP you do not need to do anything. Just create some.php files, place them in your web directory, and the server will automatically parse them for you. You do not need to compile anything or install any extra tools. Because PHP is free, most web hosts offer PHP support. Set Up PHP on Your Own PC However, if your server does not support PHP, you must: install a web server install PHP install a database, such as MySQL 4.2 PHP Scripts Basic PHP Syntax A PHP script can be placed anywhere in the document. A PHP script starts with : Example My first PHP page PHP statements end with a semicolon (;) Comments in PHP A comment in PHP code is a line that is not read/executed as part of the program. Its only purpose is to be read by someone who is looking at the code. Comments can be used to: Let others understand what you are doing Remind yourself of what you did - Most programmers have experienced coming back to their own work a year or two later and having to re-figure out what they did. Comments can remind you of what you were thinking when you wrote the code Example Example In the example below, only the first statement will display the value of the $color variable (this is because $color, $COLOR, and $coLOR are treated as three different variables): Example  4.3 Data Types Variables can store data of different types, and different data types can do different things. PHP supports the following data types: String Integer Float (floating point numbers - also called double) Boolean Array Object NULL Resource PHP String A string is a sequence of characters, like "Hello world!". A string can be any text inside quotes. You can use single or double quotes: Example OUTPUT: Hello world! Hello world! String Functions Get The Length of a String The PHP strlen() function returns the length of a string. The example below returns the length of the string "Hello world!": Example OUPUT: 12 Count The Number of Words in a String The PHP str_word_count() function counts the number of words in a string: Example OUPUT: 2 Reverse a String The PHP strrev() function reverses a string: Example OUTPUT: !dlrow olleH Search For a Specific Text Within a String The PHP strpos() function searches for a specific text within a string. If a match is found, the function returns the character position of the first match. If no match is found, it will return FALSE. The example below searches for the text "world" in the string "Hello world!": Example OUPUT: 6 Replace Text Within a String The PHP str_replace() function replaces some characters with some other characters in a string. The example below replaces the text "world" with "Dolly": Example OUPUT: Hello Dolly! PHP Integer An integer data type is a non-decimal number between -2,147,483,648 and 2,147,483,647. Rules for integers: An integer must have at least one digit An integer must not have a decimal point An integer can be either positive or negative Integers can be specified in three formats: decimal (10-based), hexadecimal (16- based - prefixed with 0x) or octal (8-based - prefixed with 0) In the following example $x is an integer. The PHP var_dump() function returns the data type and value: Example OUTPUT: int(5985) PHP Float A float (floating point number) is a number with a decimal point or a number in exponential form. In the following example $x is a float. The PHP var_dump() function returns the data type and value: Example  OUTPUT: float(10.365) PHP Boolean A Boolean represents two possible states: TRUE or FALSE. $x = true; $y = false; Booleans are often used in conditional testing. You will learn more about conditional testing in a later chapter of this tutorial. PHP Array An array stores multiple values in one single variable: An array is a special variable, which can hold more than one value at a time. If you have a list of items (a list of car names, for example), storing the cars in single variables could look like this: $cars1 = "Volvo"; $cars2 = "BMW"; $cars3 = "Toyota"; However, what if you want to loop through the cars and find a specific one? And what if you had not 3 cars, but 300? The solution is to create an array! An array can hold many values under a single name, and you can access the values by referring to an index number. Example  OUTPUT: I like Volvo, BMW and Toyota. Create an Array in PHP In PHP, the array() function is used to create an array: array(); In PHP, there are three types of arrays: Indexed arrays - Arrays with a numeric index Associative arrays - Arrays with named keys Multidimensional arrays - Arrays containing one or more arrays 4.4 Variables Variables are "containers" for storing information. Creating (Declaring) PHP Variables In PHP, a variable starts with the $ sign, followed by the name of the variable: Example After the execution of the statements above, the variable $txt will hold the value Hello world!, the variable $x will hold the value 5, and the variable $y will hold the value 10.5. Note: When you assign a text value to a variable, put quotes around the value. Note: Unlike other programming languages, PHP has no command for declaring a variable. It is created the moment you first assign a value to it. Rules for PHP variables: A variable can have a short name (like x and y) or a more descriptive name (age, carname, total_volume). A variable starts with the $ sign, followed by the name of the variable A variable name must start with a letter or the underscore character A variable name cannot start with a number A variable name can only contain alpha-numeric characters and underscores (A- z, 0-9, and _ ) Variable names are case-sensitive ($age and $AGE are two different variables) Output Variables The PHP echo statement is often used to output data to the screen. The following example will show how to output text and a variable: Example Output: Example Example PHP Variables Scope In PHP, variables can be declared anywhere in the script. The scope of a variable is the part of the script where the variable can be referenced/used. PHP has three different variable scopes: local global static Global and Local Scope A variable declared outside a function has a GLOBAL SCOPE and can only be accessed outside a function: Example OUTPUT: Variable x inside function is: Variable x outside function is: 5 A variable declared within a function has a LOCAL SCOPE and can only be accessed within that function: Example OUTPUT: Variable x inside function is: 5 Variable x outside function is: The global Keyword The global keyword is used to access a global variable from within a function. To do this, use the global keyword before the variables (inside the function): Example Output: The static Keyword Normally, when a function is completed/executed, all of its variables are deleted. However, sometimes we want a local variable NOT to be deleted. We need it for a further job. To do this, use the static keyword when you first declare the variable: Example echo and print Statements In PHP there are two basic ways to get output: echo and print. In this tutorial we use echo (and print) in almost every example. So, this chapter contains a little more info about those two output statements. echo and print are more or less the same. They are both used to output data to the screen. The differences are small: echo has no return value while print has a return value of 1 so it can be used in expressions. echo can take multiple parameters (although such usage is rare) while print can take one argument. echo is marginally faster than print. echo Statement The echo statement can be used with or without parentheses: echo or echo(). Display Text The following example shows how to output text with the echo command (notice that the text can contain HTML markup): Example