Variable Related Functions

Let's look at the functions associated with variables.

gettype

This function finds what type a variable is.
For example, a string function is a string.
If it is a number, it is a number. And so on. If the number is inside '', do you know that the computer recognizes it as a letter?

<?php
    $var = '3434';
    echo gettype($var).'<br />';
    $var = 3434;
    echo gettype($var).'<br />';
?>

settype

This function changes the type of a variable.
For example, you can change a function of a string to a number and a function of a number to a string.
The example below is a source that replaces the string 98 with a number.

<?php
    $var1 = '98';
    settype($var1, "integer");
    echo gettype($var1);
?>

intval

This function converts a variable value to an integer type.

<?php
    $var1 = 33.232;
    echo intval($var1);
?>

strval

A function that returns a variable as a character value.

<?php
    $var1 = 33;
    $var2 = strval($var1);
    echo gettype($var2);
?>

isset

This function checks whether a variable exists.

<?php
    if(isset($var)){
        echo 'exists variable';
    }else{
        echo 'non-existent variable'';
    }
?>

unset

Function to delete a variable.

<?php
    $var = 'variable';
    if(isset($var)){
        echo 'exists variable';
    }else{
        echo 'non-existent variable';
    }
    echo '<br />';
    echo '<br />';
    unset($var);
    echo 'after using unset <br />';
    echo '<br />';
    echo '<br />';
    if(isset($var)){
        echo 'exists variable';
    }else{
        echo 'non-existent variable';
    }
?>

empty

This function returns true if the value does not exist and false if it exists.

<?php
    $var = ''; // or $var = null; or $var = false

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

is_array

Checks whether a variable type is an array. Returns true if it is an array, false if it is not an array.

<?php
    $arr = array();
    if(is_array($arr)){
        echo "this is array";
    }else{
        echo "not array";
    }
?>

is_double

Returns true if the variable type is double(decimal) and false otherwise.

<?php
    $var = 23234.343;

    if(is_double($var)){
        echo 'Decimal.';
    }else{
        echo "not";
    }

?>

is_bool

Returns true if the variable type is boolean(logical speaker), false otherwise.

<?php
    $var = true;

    if(is_bool($var)){
        echo 'This is a boolean.';
    }
    echo '<br />';
    $var = false;

    if(is_bool($var)){
        echo 'This is a boolean.';
    }
?>

is_integer

Returns true if the variable type is integer(integer) and false otherwise.

<?php
    $var = 1212;
    if(is_integer($var)){
        echo 'integer type.';
    }
?>

is_null

Check if the variable is empty.

<?php
    $var = null;
    if(is_null($var)){
        echo 'The variable has no value.';
    }
 ?>

is_numeric

Check if the variable is empty.

<?php
    $var = 2323.34;
    if(is_numeric($var)){
        echo 'The value of the variable is a number.';
    }
?>

is_object

Check if the variable is empty.

<?php
    class Hello
    {
        public function helloOutput(){
            echo 'hello world';
        }
    }

    $hello = new Hello;

    if(is_object($hello)){
        echo 'This is an object.';
    }else{
        echo 'Not an object';
    }
?>

is_string

Determine if a variable is a string

<?php
    $var = 'I am a string';

    if(is_string($var)){
        echo 'This is a string.';
    }else{
        echo 'Not a string';
    }
?>