PHP parentheses usage

In PHP, parentheses serve various roles depending on their usage. They can be compulsory for code to compile correctly, optional for clarity or precedence, and sometimes completely unnecessary. They play a crucial role in function definitions, method calls, control structures, and grouping expressions. Parentheses also help in managing operator precedence and improving readability, though they can occasionally lead to confusing or redundant code. It's crucial to understand the contexts in which they are beneficial or required to write effective PHP code.