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Note for Web Technologies - WT By Ram Sunnihith

  • Web Technologies - WT
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 Variable names are case-sensitive ($age and $AGE are two different variables). PHP is a Loosely Typed Language In the example above, notice that we did not have to tell PHP which data type the variable is. PHP automatically converts the variable to the correct data type, depending on its value.In other languages such as C, C++, and Java, the programmer must declare the name and type of the variable before using it. 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: <?php $x = 5; // global scope function myTest() { // using x inside this function will generate an error echo "<p>Variable x inside function is: $x</p>"; } myTest(); echo "<p>Variable x outside function is: $x</p>"; ?> A variable declared within a function has a LOCAL SCOPE and can only be accessed within that function: <?php function myTest() {

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$x = 5; // local scope echo "<p>Variable x inside function is: $x</p>"; } myTest(); // using x outside the function will generate an error echo "<p>Variable x outside function is: $x</p>"; ?> PHP 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: <?php $x = "Hello world!"; $y = 'Hello world!'; echo $x; echo "<br>"; echo $y; ?> PHP Integer An integer is a whole number (without decimals). It is a number between -2,147,483,648 and +2,147,483,647.

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Rules for integers:  An integer must have at least one digit (0-9)  An integer cannot contain comma or blanks  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: <?php $x = 5985; var_dump($x); ?> 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: <?php $x = 10.365; var_dump($x); ?> PHP Boolean A Boolean represents two possible states: TRUE or FALSE. $x = true; $y = false; PHP Array An array stores multiple values in one single variable. In the following example $cars is an array. The PHP var_dump() function returns the data type and value: <?php $cars = array("Volvo","BMW","Toyota"); var_dump($cars); ?>

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PHP NULL Value Null is a special data type which can have only one value: NULL. A variable of data type NULL is a variable that has no value assigned to it. Array 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. Create an Array in PHP In PHP, the array() function is used to create an 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 PHP Indexed Arrays There are two ways to create indexed arrays: The index can be assigned automatically (index always starts at 0), like this: $cars = array("Volvo", "BMW", "Toyota"); The following example creates an indexed array named $cars, assigns three elements to it, and then prints a text containing the array values: <?php $cars = array("Volvo", "BMW", "Toyota"); echo "I like " . $cars[0] . ", " . $cars[1] . " and " . $cars[2] . "."; ?>

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