What will be the output of the following PHP code?

<?php
$value = 'car';
$result = filter_var($value, FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE);
?>

A. FALSE

B. TRUE

C. NULL

D. ERROR

Answer: Option C

Solution(By Examveda Team)

There is an undocumented filter flag for FILTER_VALIDATE_BOOLEAN. The documentation implies that it will return NULL if the value doesn’t match the allowed true/false values. However this doesn’t happen unless you give it the FILTER_NULL_ON_FAILURE flag.