What is the significance of using single quotes around table and column names in SQL queries in PHP?

When writing SQL queries in PHP, using single quotes around table and column names is important to ensure that the query is syntactically correct. This is necessary because SQL treats table and column names as identifiers, and using single quotes helps to differentiate them from string values. Failure to use single quotes can result in syntax errors or unexpected behavior in the query execution.

// Example of using single quotes around table and column names in an SQL query
$table = 'users';
$column = 'username';

$sql = "SELECT $column FROM $table WHERE id = 1";