PHP Best Practices----detect whether a value is null or FALSE

Use the = = = operator to detect null and Boolean false values.

PHP's loose type system provides many different ways to detect a variable's value. However, this has caused a lot of problems. Use = = to detect whether a value is null or FALSE, and false if the value is actually an empty string or 0. Isset is not appropriate to detect whether a variable has a value, rather than detecting whether the value is null or FALSE.

The Is_null () function can accurately detect whether a value is Null,is_bool can detect whether a value is a Boolean value (such as false), but there is a better choice: = = operator. = = = Detect whether two values are the same, which is different from the equivalent in the PHP loose type world. It's also faster than Is_null () and Is_bool (), and some people think it's a bit cleaner than using a function.

Example

<?php
$x = 0;
$y = null;

is $x null?
if ($x = = null)
    print (' oops! $x is 0, not null! ');

is $y null?
if (Is_null ($y))
    print (' great, but could be faster. ');

if ($y = = null)
    print (' perfect! ');

Does the string ABC contain the character a?
if (Strpos (' abc ', ' A '))
    //gotcha!  Strpos returns 0, indicating it wishes to return the position of the the ' the ' the ' the ' the '.
    But PHP Interpretes 0 as false, so we never to this print statement!
    Print (' Found it! ');

Solution:use!== (the opposite of = =) to the If Strpos () returns 0, or Boolean false.   
if (Strpos (' abc ', ' A ')!== false)
    print (' Found it for Real this time! ');
? >

Traps test a return value for a function that returns 0 or Boolean false, such as Strpos (), always use = = = and!==, otherwise you will encounter problems.