How can syntax errors, such as missing variables or incorrect comparison operators, impact the functionality of conditional statements in PHP?

Syntax errors in conditional statements can prevent the code from running correctly, leading to unexpected behavior or errors. Missing variables can cause undefined variable errors, while incorrect comparison operators can result in incorrect logic being applied. To fix these issues, ensure that all variables are properly defined and that comparison operators are used correctly within the conditional statements.

// Incorrect comparison operator
$age = 25;

if ($age = 18) {
    echo "You are an adult.";
}

// Corrected code with comparison operator ==
$age = 25;

if ($age == 18) {
    echo "You are an adult.";
}