What is the common error message "Invalid argument supplied for foreach()" in PHP and how can it be resolved?

The "Invalid argument supplied for foreach()" error in PHP occurs when you try to loop through a variable using foreach() that is not an array or an object that implements the Traversable interface. To resolve this issue, you should check if the variable is an array or an object before using foreach().

// Check if the variable is an array or an object before using foreach()
if(is_array($variable) || $variable instanceof Traversable) {
    foreach($variable as $item) {
        // Loop through the variable
    }
} else {
    // Handle the case when the variable is not iterable
    echo "Invalid argument supplied for foreach()";
}