How can PHP developers ensure that variables are properly replaced in text outputs, as discussed in the thread?

To ensure that variables are properly replaced in text outputs in PHP, developers can use double quotes instead of single quotes when defining strings that contain variables. This allows for variable interpolation, where the variables are replaced with their respective values in the output. Additionally, developers can concatenate variables with strings using the dot (.) operator to ensure proper replacement.

$name = 'John';
$age = 30;

// Using double quotes for variable interpolation
echo "My name is $name and I am $age years old.";

// Using concatenation for variable replacement
echo 'My name is ' . $name . ' and I am ' . $age . ' years old.';