What is the error message "Parse error: syntax error, unexpected ''1'' (T_CONSTANT_ENCAPSED_STRING)" indicating in the provided PHP code?

The error message "Parse error: syntax error, unexpected ''1'' (T_CONSTANT_ENCAPSED_STRING)" indicates that there is a syntax error in the PHP code where a constant string is not properly enclosed within quotes. To fix this issue, you need to ensure that all string values are enclosed within single or double quotes. Here is a corrected PHP code snippet:

$name = "John";
echo "Hello, $name!";