What is the difference between a variable assignment and a comparison in PHP, and how does it affect conditional statements?

In PHP, a variable assignment is when you assign a value to a variable using the assignment operator "=", while a comparison is when you compare two values using comparison operators like "==", ">", "<", etc. When writing conditional statements in PHP, it's important to use comparison operators to compare values and make decisions based on the comparison result. Using variable assignments in conditional statements can lead to unexpected behavior as it assigns a value to a variable rather than comparing values.

// Incorrect usage of variable assignment in a conditional statement
$age = 25;
if ($age = 18) {
    echo "You are an adult.";
}

// Correct usage of comparison in a conditional statement
$age = 25;
if ($age == 18) {
    echo "You are an adult.";
}