The is_null() function is an inbuilt function in PHP which is used to find whether a variable is NULL or not.
Syntax:
boolean is_null ( $var )
Parameters: This function accepts a single parameter as shown in above syntax and described below.
- $var: Variable to check if it is NULL or not.
Return value: It returns a boolean value. That is, it returns TRUE when $var will be NULL, otherwise it returns FALSE.
Below programs illustrate the is_null() function in PHP:
Program 1:
PHP
<?php// PHP code to demonstrate the working of is_null() function$var1 = NULL;$var2 = "\0"; // "\0" means "\0"$var3 = "NULL";$var4 = 0;// $var1 has NULL value, so always give TRUEis_null($var1) ? print_r("True\n") : print_r("False\n");// $var2 has '\0' value which consider as null in // c and c++ but here taken as string, gives FALSEis_null($var2) ? print_r("True\n") : print_r("False\n");// $var3 has NULL string value so it will falseis_null($var3) ? print_r("True\n") : print_r("False\n");// $var4 is 0, gives FALSEis_null($var4) ? print_r("True\n") : print_r("False\n");?> |
Output:
True False False False
Program 2:
PHP
<?php// PHP code to demonstrate the working of// is_null() functionfunction check_null($var){ return (is_null($var) ? "True" : "False");}echo check_null(NULL) . "\n"; echo check_null(null) . "\n"; echo check_null(Null) . "\n"; echo check_null(NUll) . "\n"; echo check_null(NULl) . "\n"; echo check_null(nulL) . "\n"; echo check_null(nuLL) . "\n"; echo check_null(nULL) . "\n"; echo check_null(Nul) . "\n"; echo check_null(false) . "\n"; ?> |
Output:
True True True True True True True True False False
