In this tutorial you will come to know about NULL values and how to make a variable NULL, how to check a variable etc.
In this tutorial you will come to know about NULL values and how to make a variable NULL, how to check a variable etc.PHP NULL type:
In PHP 4 a special type of value is introduced, which indicates that a variable does not consists of any value or NULL value. NULL is the only value of NULL datatype.
A variable is considered to be NULL if we use unset() method on a variable, or a NULL value is assigned to the variable, no value is yet assigned to it.
Two special functions are used in this context, is_null() and unset(). is_null() function is used to check whether a variable is NULL assigned or it has some value.
PHP Null Type Example:
<?php
$a;
echo "1=True and Blank=False".is_null($a)."<br/>";
$a=23;
echo "1=True and Blank=False".is_null($a)."<br/>";
$a=NULL;
echo "1=True and Blank=False".is_null($a)."<br/>";
$a=12;
echo "1=True and Blank=False".is_null($a)."<br/>";
unset($a);
echo "1=True and Blank=False".is_null($a)."<br/>";
?>
Output:
1=True and Blank=False1
1=True and Blank=False
1=True and Blank=False1
1=True and Blank=False
1=True and Blank=False1