What are the potential pitfalls of using string concatenation with variables in PHP?

Using string concatenation with variables in PHP can lead to messy and hard-to-read code, especially when dealing with multiple variables. It can also be less efficient than using double quotes for string interpolation. To solve this issue, you can use double quotes to directly insert variables into a string without the need for concatenation.

// Example of using double quotes for string interpolation
$name = "John";
$age = 30;
echo "My name is $name and I am $age years old.";