PHP/MySQL Checking for null - php

Question

$sql = 'SELECT * FROM `phpbb_profile_fields_data`';
$result = $db->sql_query($sql);
while ($row = $db->sql_fetchrow($result)) {
if ($row['pf_kp_em_no_bonethr'] == '1') {
echo " Was 1";
} else if ($row['pf_kp_em_no_bonethr'] == '2') {
echo "Was 2";
} else {
echo "Was Neither 1 or 2";
}
}
$db->sql_freeresult($result);
I am curios, In my example I am checking the field for either a value of 1 or 2 but how do I check it for a value of NULL. Would it be any of the following three:
if ($row['pf_kp_em_no_bonethr'] == '')
if ($row['pf_kp_em_no_bonethr'] == '-1')
if ($row['pf_kp_em_no_bonethr'] == 'NULL')
Normally I would just try it out but I am not at home and wont be for the foreseeable future it has been bugging me. I am pretty sure it's not the second but I have seen -1 used for a null value in other languages. So can someone verify how I would indeed check for a NULL value please.

Answer 1

if ($row['pf_kp_em_no_bonethr'] === NULL)

Answer 2

Something like this should work.
if (is_null($row['pf_kp_em_no_bonethr'])) {
echo "Is NULL";
}

Answer 3

MySQL will return NULL values to PHP as actual PHP NULL. In this situation, what you need is:
// Notice lack of quotes around NULL
// And use === to distinguish type properly between integer 0 and NULL
if ($row['pf_kp_em_no_bonethr'] === NULL)
However, it would be more appropriate to check it in the query if NULL values are what you need to work with in PHP.
$sql = 'SELECT * FROM `phpbb_profile_fields_data` WHERE pf_kp_em_no_bonethr IS NULL';
Or to find all three values:
$sql = 'SELECT * FROM `phpbb_profile_fields_data`
WHERE pf_kp_em_no_bonethr IS NULL
OR pf_kp_em_no_bonethr IN (1,2)
';

Answer 4

I'd recommend to be very carfull with this one: I have seen
<?php
$field=$row['fieldname'];
if ($field===null) {
//Do something
}
?>
fail intermittently, especially on windows. This is why I prefer
SELECT
IFNULL(fieldname,'some_safe_value') AS fieldname
...
FROM
...
and the resulting trivial null-check.

Answer 5

Use is_null or === NULL.
if(is_null($row['pf_kp_em_no_bonethr'])){
}
or
if($row['pf_kp_em_no_bonethr'] === NULL){
}