What is the significance of the error message "First argument is expected to be a valid callback, 'Array' was given" in the context of PHP usage?

The error message "First argument is expected to be a valid callback, 'Array' was given" typically occurs when a function in PHP is expecting a callback function as its first argument, but an array is passed instead. To solve this issue, you need to ensure that you are passing a valid callback function to the function that requires it. 

// Incorrect usage causing the error
$callback = array('ClassName', 'methodName');
usort($array, $callback);

// Correct usage with a valid callback function
function customSort($a, $b) {
    return strcmp($a, $b);
}
usort($array, 'customSort');

Keywords

PHP error message callback Array significance

Related Questions