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PHP Data Types

Data type is used to specify the type of data that variable can hold. A variable’s data type determines what operations can be carried out on the variable’s data, as well as the amount of memory needed to hold the data.

In PHP we have 3 types of data types.

1. Scalar

2. Compound

3. Special

Scalar Data types

Boolean

Boolean data type represents either true or false. In PHP value of true is 1 and the value of false is nothing.

<?php

$boolean_var = true;

echo $boolean_var;

?>

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is_bool(variable)

is_bool function is used to check if variable is boolean variable.

Type casting to Boolean

Below is the syntax to convert variables of other type to boolean type.

(boolean)variableName;

OR

(bool)variableName;

<?php

$boolean_var = true;

echo $boolean_var."</br>";

echo is_bool($boolean_var)."</br>";

 

$string_var = "true";

$string_to_boolean_var = (bool)$string_var;

echo $string_var."</br>";

echo $string_to_boolean_var."</br>";

?>

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Integer

Integer data type represents numeric values.

is_int(variable)/is_interger (variable)

is_int/is_integer function is used to check if variable is integer variable.

Type casting to integer

Below is the syntax to convert variables of other type to integer type.

(int)variableName;

OR

(integer)variableName;

<?php

$integer_var = 123;

echo is_int($integer_var)."</br>";

 

$string_var = "10";

$string_to_integer_var = (int)$string_var;

echo $string_to_integer_var."</br>";

?>

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Float

Float data type represents decimal values.

is_float(variable)

is_float function is used to check if variable is float variable.

Type casting to float

Below is the syntax to convert variables of other type to float type.

(float)variableName;

<?php

$float_var = 123.10;

echo is_float($float_var)."</br>";

 

$string_var = "10.10";

$string_to_float_var = (float)$string_var;

echo $string_to_float_var."</br>";

?>

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String

String is group of any characters. String can contain any alphabets, numbers, special characters.

In PHP you can declare string variable in 3 ways.

  1. Using single quotes 

  2. Using double quotes 

  3. Using heredoc syntax 

String using single quotes

Strings are created inside single quotes.

<?php

$name = 'Manu Manjunatha';

?>

String using double quotes

Strings are created inside double quotes.  String using double quotes supports interpolation, means if you place a variable within the double quotes, it returns the value of that variable. You can place the variable name directly inside double quotes or you can use interpolation syntax ${variableName} as below example.

<?php

$name = 'Manu Manjunatha';

 

echo "My name is $name </br>";

echo 'My name is $name </br>';

echo "My name is ${name} </br>";

echo 'My name is ${name} </br>';

 

?>

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String using heredoc syntax

The heredoc syntax is useful for multi-line strings and avoiding quoting issues.  Below is the heredoc syntax:

$variable = <<<nameOfString

//contents

nameOfString;

 

String using heredoc syntax supports interpolation, means if you place a variable within a string, it returns the value of that variable. You can place the variable name directly inside double quotes or you can use interpolation syntax ${variableName} as below example.

heredoc string example:

<?php

$author= "Manu Manjunatha";

$tablename = "Student";

$id = 100;

 

$sql = <<<SQL

select *

  from $tablename

 where studenid = $id

   and studentname = $author

SQL;

 

 

$html = <<<HTML

</br><b>Welcome to www.java4coding.com</b> </br>

<p>Author: ${author}</p>

<p>Author Id: ${id}</p>

HTML;

 

echo $sql."</br>";

echo $html;

?>

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Compound data types

Array

  • PHP array is collection of values of heterogeneous (dissimilar) same data type.  

  • array() function is used to create an array.   

$array_name = array(element1, element2, element3, …);

  • Array index starts form 0. Below is the syntax of access array element: 

$array_name[index];

  • count() function is used to get the size of array. 

<?php

$array_var = array("Mango", "Apple", 100, true);

echo  $array_var[0] . ", " . $array_var[1] . ", ". $array_var[2] . ", " .$array_var[3]."</br>";

echo "Array size: ". count($array_var);

?>

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Objects

Objects are the instances of class. You will learn about classes in later chapters.

<?php

class welcome{

    public $var="Welcome to www.java4coding.com";

    function show_msg(){

        return $this->var;

    }

}

 

//create object from the class

$welcome_msg=new welcome;

var_dump($welcome_msg);

?>

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Special data types

Resource data type

Resource data type represents an access to external resources like database, files etc...

<?php

$conn = mysqli_connect(localhost,"root","admin","password");

$fp = fopen("index.php",'r');

?>

null data type

null is not a value, variable is considered as null based on below 3 conditions

1. If variable is not initialized with value.

2. If variable is set with Null explicitly.

3. If the value of variable is unset using unset function;

<?php

$a=null;

echo is_null($a);

 

$b;

echo is_null($b);

 

$c=10;

unset($c);

echo is_null($c);

?>

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