What common errors can occur when using fopen() to open a file in PHP?

One common error when using fopen() in PHP is not checking if the file was successfully opened before performing operations on it. This can lead to errors if the file does not exist or if there are permission issues. To solve this, always check the return value of fopen() to ensure the file was opened successfully before proceeding with any file operations.

$file = fopen("example.txt", "r");
if ($file) {
    // File opened successfully, perform operations here
    fclose($file);
} else {
    echo "Error opening file.";
}