PHP Variable function
1- empty()

This function check whether a variable is empty or not.

Note : - Return false if variable has a non_empty and non-zero value. Return true if variable has empty or zero.

Return Type:- bool

<?php
$var = 30;

if (empty($var))
{
echo \"Varible is empty\";
}
else
{
echo \"Varible is not empty\";
}
?>

Output:-
Varible is not empty
2- isset()

This function check whether variable exists or not. Return True if variable exists otherwise return False.

Note : - isset function is very usefull for check $_Post[\'btnsubmit\'], $_Get[\'btnsubmit\'] etc variable.

Return Type:- bool

<?php

$var = 30;

if (isset($var))
{
echo \"Varible is exist\";
}
else
{
echo \"Varible is not exist\";
}

?>

Output :-
Varible is exist

3- unset()

This function destroy variables.

Note :- You can use unset function to destroy session varaibles.

Return Type :- void

<?php

$var = 30;

echo $var;

unset($var);

echo $var;

?>

Output :-
30

4- print_r()

This function display information about variable.

Return Type :- bool

<?php
$my_array = array(5,6,7,8);
print_r($my_array);
?>

Output :-
Array ( [0] => 5 [1] => 6 [2] => 7 [3] => 8 )

5- intval()

This function returns the integer value of the variable.

Return Type :- int

<?php
echo intval(45.67);
echo \"<br>\";
echo intval(-67.45);
?>


Output :
45
-67

6- gettype()

 This function returns the type of variable.

Return Type :- string

<?php
$x=\"welcome\";
$y=56;
$z=56.34;
echo gettype($x);
echo \"<br>\";
echo gettype($y);
echo \"<br>\";
echo gettype($z);
?>

Output :
string
integer
double

7- settype()

This function returns convert variable datatype.

Return Type :- bool

<?php
$x=\"welcome\";
$y=56;
$z=56.34;
settype($x,\"integer\");
echo gettype($x);
echo \"<br>\";
settype($y,\"boolean\");
echo gettype($y);
echo \"<br>\";
settype($z,\"double\");
echo gettype($z);
?>

Output :
integer
boolean
double

8- strval()

This function convert a value of the variable to the string.

Return Type :- string

Example :-

<?php
$num=5;
$str=strval($num);
echo gettype($num).\"<br>\";
echo gettype($str);
?>

Output :-
integer
string

9- var_dump()

This function provide us dumps information of variable.

Return Type :- void

Example :-

<?php
$x=\"This is test string\";
$a = array(34, 62, array(\"sun\", \"mon\", \"tue\"));
var_dump($x);
var_dump($a);
?> 

Output :-

string \'This is test string\' (length=19)
array
  0 => int 34
  1 => int 62
  2 => 
    array
      0 => string \'sun\' (length=3)
      1 => string \'mon\' (length=3)
      2 => string \'tue\' (length=3)

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