What does the error message "Parse error: parse error, unexpected T_STRING" indicate in PHP?

The error message "Parse error: parse error, unexpected T_STRING" in PHP indicates that there is a syntax error involving a string literal in the code. This often occurs when a string is not properly enclosed in quotes or when there is a mismatch in the quotes used. To solve this issue, check the string literals in your code and ensure they are correctly enclosed in single or double quotes.

// Incorrect code causing the parse error
$message = Hello World!;

// Corrected code with the string enclosed in double quotes
$message = "Hello World!";