How to Correctly Check for NULL Values in PHP?

PHP NULL Value Check

In PHP, NULL values can be a source of unexpected behavior while working with database queries and manipulating data.

Consider the following code:

<code class="php">$query = mysql_query("SELECT * FROM tablex");

if ($result = mysql_fetch_array($query)) {
    if ($result['column'] == NULL) { print "<input type='checkbox' />"; }
    else { print "<input type='checkbox' checked />"; }
}</code>

Here, it is expected that if the value of $result['column']'' is NULL, an unchecked checkbox should be printed. However, if the value is not NULL, an unchecked checkbox is still printed.

To correctly check for NULL values, two alternative operators can be used:

1. is_null() Function

The is_null() function explicitly checks if a variable or array element is NULL.

<code class="php">if (is_null($result['column'])) {
    // Code to execute when the value is NULL
} else {
    // Code to execute when the value is not NULL
}</code>

2. === Operator

The === operator provides a strict comparison, ensuring that the type of the value on the left-hand side is identical to that on the right-hand side. This is recommended over the == operator, which only checks for equality of values.

<code class="php">if ($result['column'] === NULL) {
    // Code to execute when the value is NULL
} else {
    // Code to execute when the value is not NULL
}</code>

Using either is_null() or the === operator will accurately determine whether the value of result['column']]'' is NULL or not and will allow you to handle NULL values appropriately in your code.

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