PHP Tutorial: PHP Variable types

The main thanks to store info within the middle of a PHP program is by employing a variable.

Here square measure the foremost necessary things to grasp regarding variables in PHP.

All variables in PHP square measure denoted with a number one dollar sign ($).

The worth of a variable is that the value of its most up-to-date assignment.

Variables square measure appointed with the = operator, with the variable on the left-hand aspect and therefore the expression to be evaluated on the correct.

Variables will, however don't want, to be declared before assignment.

Variables in PHP don't have intrinsic sorts - a variable doesn't grasp ahead whether or not it'll be accustomed store variety or a string of characters.

Variables used before they're appointed have default values.

PHP will a decent job of mechanically changing sorts from one to a different once necessary.

PHP variables square measure Perl-like.

PHP contains a total of eight knowledge sorts that we tend to use to construct our variables:

Integers: square measure whole numbers, while not a percentage point, like 4195.

Doubles: square measure floating-point numbers, like 3.14159 or forty nine.1.

Booleans: have solely 2 doable values either true or false.

NULL: could be a special sort that solely has one value: NULL.

Strings: square measure sequences of characters, like 'PHP supports string operations.'

Arrays: square measure named and indexed collections of different values.

Objects: square measure instances of programmer-defined categories, which may package up each other forms of values and functions that square measure specific to the category.

Resources: square measure special variables that hold references to resources external to PHP (such as info connections).

The first 5 square measure straightforward sorts, and therefore the next 2 (arrays and objects) square measure compound - the compound sorts will package up different arbitrary  values of arbitrary  sort, whereas the easy sorts cannot.

We will justify solely figure knowledge sort during this chapters. Array and Objects are going to be explained individually.

Integers:

They are whole numbers, while not a percentage point, like 4195. they're the only sort .they correspond to straightforward whole numbers, each positive and negative. Integers may be appointed to variables, or they'll be employed in expressions, like so:

$int_var = 12345;
$another_int = -12345 + 12345;

Integer are often in decimal (base 10), positional representation system (base 8), and positional representation system (base 16) format. Decimal format is that the default, positional representation system integers square measure given with a number one zero, and hexadecimals have a number one 0x.

For most common platforms, the biggest number is (2**31 . 1) (or 2,147,483,647), and also the smallest (most negative) number is . (2**31 . 1) (or .2,147,483,647).

Doubles:

They like three.14159 or forty nine.1. By default, doubles print with the minimum variety of decimal places required. for instance, the code:

$many = 2.2888800;
$many_2 = 2.2111200;
$few = $many + $many_2;
print(.$many + $many_2 = $few<br>.);

In your browser it will show like this:

2.28888 + 2.21112 = 4.5

Boolean:

They have solely 2 doable values either true or false. PHP provides a few of constants particularly to be used as Booleans: TRUE and FALSE, which may be used like so:

if (TRUE)
   print("This will always print<br>");
else
   print("This will never print<br>");

Interpreting alternative sorts as Booleans:

Here square measure the foundations for confirm the "truth" of any worth not already of the mathematician type:

If the worth could be a range, it's false if specifically adequate to zero and true otherwise.

If the worth could be a string, it's false if the string is empty (has zero characters) or is that the string "0", and is true otherwise.

Values of kind NULL square measure continuously false.

If the worth is associate array, it's false if it contains no alternative values, and it's true otherwise. For associate object, containing a worth means that having a member variable that has been allotted a worth.

Valid resources square measure true (although some functions that come back resources after they square measure prospering can come back FALSE once unsuccessful).

Don't use double as Booleans.

Each of the subsequent variables has the reality worth embedded in its name once it's employed in a mathematician context.

$true_num = 3 + 0.14159;
$true_str = "Tried and true"
$true_array[49] = "An array element";
$false_array = array();
$false_null = NULL;
$false_num = 999 - 999;
$false_str = "";

NULL:

NULL could be a special kind that solely has one value: NULL. to administer a variable the NULL price, merely assign it like this:

$my_var = NULL;

The special constant NULL is capitalized by convention, however truly it's case insensitive; you'll even as well have typed:

$my_var = null;

A variable that has been allotted NULL has the subsequent properties:

It evaluates to FALSE in an exceedingly mathematician context.

It returns FALSE once tested with IsSet() operate.

Strings:

They are sequences of characters, like "PHP supports string operations". Following area unit valid samples of string

$string_1 = "This is a string in double quotes";
$string_2 = "This is a somewhat longer, singly quoted string";
$string_39 = "This string has thirty-nine characters";
$string_0 = ""; // a string with zero characters

Singly quoted strings square measure treated virtually virtually, whereas doubly quoted strings replace variables with their values moreover as specially deciphering bound character sequences.

<? $variable = "name"; $literally = 'My $variable will not print!\\n'; print($literally); $literally = "My $variable will print!\\n"; print($literally); ?>

This will bring you this result:

My $variable will not print!\n
My name will print

There aren't any artificial limits on string length - inside the bounds of obtainable memory, you need to be able to create at random long strings.

Strings that area unit delimited by quotation mark (as in "this") area unit preprocessed in each the subsequent 2 ways in which by PHP:

Certain character sequences starting with backslash (\) area unit replaced with special characters

Variable names (starting with $) area unit replaced with string representations of their values.

The escape-sequence replacements are:

\n is replaced by the newline character

\r is replaced by the carriage-return character

\t is replaced by the tab character

\$ is replaced by the greenback sign itself ($)

\" is replaced by one double-quote (")

\\ is replaced by one backslash (\)

Here Document:

You can assign multiple lines to one string variable exploitation here document:

<?php

$channel =<<<_XML_
<channel>
<title>What's For Dinner<title>
<link>http://menu.example.com/<link>
<description>Choose what to eat tonight.</description>
</channel>
_XML_;

echo <<<END
This uses the "here document" syntax to output
multiple lines with variable interpolation. Note
that the here document terminator must appear on a
line with just a semicolon. no extra whitespace!
<br />
END;

print $channel;
?>

Now you will have this result:

This uses the "here document" syntax to output
multiple lines with variable interpolation. Note
that the here document terminator must appear on a
line with just a semicolon. no extra whitespace!

<channel>
<title>What's For Dinner<title>
<link>http://menu.example.com/<link>
<description>Choose what to eat tonight.</description>

Variable Scope:

Scope will be outlined because the vary of available a variable needs to the program during which it's declared. PHP variables will be one in all four scope types:

Local variables:
http://www.tutorialspoint.com/php/php_local_variables.htm

Function parameters:
http://www.tutorialspoint.com/php/php_function_parameters.htm

Global variables:
http://www.tutorialspoint.com/php/php_global_variables.htm

Static variables:
http://www.tutorialspoint.com/php/php_static_variables.htm

Variable Naming:

Rules for naming a variable is:

Variable names should begin with a letter or underscore character.

A variable name will incorporates numbers, letters, underscores however you can not use characters like + , - , % , ( , ) . & , etc

There is no size limit for variables.