What does the warning "expects parameter 1 to be resource" mean in PHP?

The warning "expects parameter 1 to be resource" in PHP typically occurs when a function is expecting a resource type argument, such as a file handle or database connection, but is receiving a different type of data. To solve this issue, you need to make sure that you are passing the correct type of data to the function. One common mistake that leads to this warning is passing a variable that is not a valid resource type. Check the documentation of the function to see what type of data it expects and make sure you are providing the correct type.

// Incorrect usage that may trigger the warning
$data = "example data";
$resource = fopen("example.txt", "r");
$result = someFunction($data); // This may trigger the warning

// Correct usage without triggering the warning
$data = "example data";
$resource = fopen("example.txt", "r");
$result = someFunction($resource); // Pass the resource variable instead