How important is it to use quotation marks in PHP code, and what impact can it have on functionality?

Using quotation marks in PHP code is crucial for correctly defining strings and preventing syntax errors. Omitting or using the wrong type of quotation marks can lead to unexpected behavior or errors in your code. It is important to use single or double quotation marks consistently throughout your code to ensure proper functionality.

// Incorrect usage of quotation marks
$variable = 'Hello"; // This will result in a syntax error

// Correct usage of quotation marks
$variable = 'Hello'; // This will define the string correctly