What are the differences between using single-line conditional statements in PHP with or without curly braces, and how does it impact code readability and maintainability?

Using single-line conditional statements in PHP without curly braces can lead to potential issues with code readability and maintainability. It can be unclear where the conditional statement begins and ends, especially when multiple statements are nested. To improve readability and maintainability, it is recommended to always use curly braces even for single-line conditional statements.

// Incorrect way without curly braces
if ($condition) 
    echo "Condition is true";

// Correct way with curly braces
if ($condition) {
    echo "Condition is true";
}