w3resource

PHP: unset() function

Description

The unset() function destroys a given variable.

Version:

(PHP 4 and above)

Syntax:

unset (var1, var2.... )

Parameters:

Name Description Required /
Optional
Type
var1 The variable to be unset. Required Mixed*
var2 Another variable to be unset Optional Mixed*

*Mixed: Mixed indicates that a parameter may accept multiple (but not necessarily all) types.

Return value:

No value is returned.

Example - 1:

<?php
$xyz='w3resource.com';
echo 'Before using unset() the value of $xys is : '. $xyz.'<br>';
unset($xyz);
echo 'After using unset() the value of $xys is : '. $xyz;
?>

Output :

Before using unset() the value of $xys is : w3resource.com
After   using unset() the value of $xys is : 

View the example in the browser

Practice here online :

Example - 2 :

<?php
function destroy_variable()
{
unset($GLOBALS['w3resource']);
}
$w3resource='Php Tutorial';
destroy_variable();
echo $w3resource;
?> 
    

View the example in the browser

See also

PHP Function Reference

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Next: var_dump



PHP: Tips of the Day

SQL injection that gets around mysql_real_escape_string()

Consider the following query:

$iId = mysql_real_escape_string("1 OR 1=1");    
$sSql = "SELECT * FROM table WHERE id = $iId";

mysql_real_escape_string() will not protect you against this. The fact that you use single quotes (' ') around your variables inside your query is what protects you against this. The following is also an option:

$iId = (int)"1 OR 1=1";
$sSql = "SELECT * FROM table WHERE id = $iId";

Ref : https://bit.ly/32q3bJ7