Why does PHP report an empty string as NULL when using the == operator?

Why Is PHP Reporting NULL for Empty Strings?

In PHP, using the == operator for comparison may lead to unexpected results when dealing with empty values.

Consider the following code:

<code class="php">$a = '';
if($a == NULL) {
    echo 'is null';
}</code>

Surprisingly, this code will output "is null" despite $a being an empty string.

The Reason

The == operator performs type coercion and compares values of different types. In this case, $a (an empty string) is converted to its boolean equivalent, which is false. false is considered equivalent to NULL in PHP when using ==.

The Solution

To accurately compare for NULL, use the strict equality operator === instead of ==.

<code class="php">if($a === NULL) {
    echo 'is null';
}</code>

The === operator performs type-safe comparisons and will return true only if the values are identical in both value and type.

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