What are common mistakes when using isset() in PHP and how can they be avoided?

Common mistakes when using isset() in PHP include not checking if the variable is set before using it, not using isset() properly in conditional statements, and assuming isset() will return true for variables with empty values. To avoid these mistakes, always check if a variable is set before using it, use isset() in conditional statements to ensure the variable exists, and remember that isset() will return false for variables with empty values.

// Incorrect usage of isset()
if(isset($variable)){
    echo $variable;
}

// Corrected usage of isset()
if(isset($variable)){
    echo $variable;
}