String, Integer, Floating point numbers, Boolean, Array, Object, NULL.
PHP Strings
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
<?php
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$x = "Hello world!"; |
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echo $x; |
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echo "<br>"; |
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$x = 'Hello world!'; |
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echo $x; |
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?>
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PHP Integers
An integer is a number without decimals.
Rules for integers:
An integer must have at least one digit (0-9)
An integer cannot contain comma or blanks
An integer must not have a decimal point
An integer can be either positive or negative
Integers can be specified in three formats: decimal (10-based), hexadecimal (16-based – prefixed with 0x) or octal (8-based – prefixed with 0)
In the following example we will test different numbers. The PHP var_dump() function returns the data type and value of variables:
Example
<?php
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$x = 5985; |
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var_dump($x); |
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echo "<br>"; |
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$x = -345; // negative number |
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var_dump($x); |
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echo "<br>"; |
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$x = 0x8C; // hexadecimal number |
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var_dump($x); |
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echo "<br>"; |
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$x = 047; // octal number |
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var_dump($x); |
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?>
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PHP Floating Point Numbers
A floating point number is a number with a decimal point or a number in exponential form.
In the following example we will test different numbers. The PHP var_dump() function returns the data type and value of variables:
Example
<?php
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$x = 10.365; |
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var_dump($x); |
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echo "<br>"; |
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$x = 2.4e3; |
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var_dump($x); |
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echo "<br>"; |
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$x = 8E-5; |
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var_dump($x); |
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?>
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PHP Booleans
Booleans can be either TRUE or FALSE.
$x=true;
$y=false;
Booleans are often used in conditional testing. You will learn more about conditional testing in a later chapter of this tutorial.
PHP Arrays
An array stores multiple values in one single variable.
In the following example we create an array, and then use the PHP var_dump() function to return the data type and value of the array:
Example
<?php
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$cars=array("Volvo","BMW","Toyota"); |
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var_dump($cars); |
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?>
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You will learn a lot more about arrays in later chapters of this tutorial.
PHP Objects
An object is a data type which stores data and information on how to process that data.
In PHP, an object must be explicitly declared.
First we must declare a class of object. For this, we use the class keyword. A class is a structure that can contain properties and methods.
We then define the data type in the object class, and then we use the data type in instances of that class:
Example
<?php
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class Car
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{
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var $color; |
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function Car($color="green") { |
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$this->color = $color; |
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}
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function what_color() { |
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return $this->color; |
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}
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}
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?>
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You will learn more about objects in a later chapter of this tutorial.
PHP NULL Value
The special NULL value represents that a variable has no value. NULL is the only possible value of data type NULL.
The NULL value identifies whether a variable is empty or not. Also useful to differentiate between the empty string and null values of databases.
Variables can be emptied by setting the value to NULL:
Example
<?php
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$x="Hello world!"; |
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$x=null; |
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var_dump($x); |
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?>
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