What are the potential pitfalls of merging variables in PHP?

Merging variables in PHP can lead to unexpected results if the variables have conflicting data types or values. To avoid this pitfall, it's important to properly sanitize and validate the input before merging variables. Additionally, using type casting or strict comparison operators can help ensure that the merged variables behave as expected.

// Example of safely merging variables in PHP
$var1 = "10";
$var2 = 5;

// Ensure both variables are integers before merging
$var1 = (int) $var1;
$var2 = (int) $var2;

$result = $var1 + $var2;

echo $result; // Output: 15