What is the significance of the error message "Warning: fopen() expects at least 2 parameters, 1 given" in PHP and how can it be resolved?

The error message "Warning: fopen() expects at least 2 parameters, 1 given" in PHP indicates that the fopen() function is missing the required second parameter, which is the mode in which the file should be opened (e.g., "r" for reading, "w" for writing). To resolve this issue, simply provide the missing second parameter when calling the fopen() function.

$file = fopen("example.txt", "r");