PHP SplObjectStorage valid() Function

<?php

// Create an empty SplObjectStorage
$str = new SplObjectStorage();

$obj = new StdClass;
$obj2 = new StdClass;
$obj3 = new StdClass;

// Use attach() function to
// add object
$str->attach($obj, "GFG");

// Use rewind() function to rewind the 
// iterator to the first storage element
$str->rewind();

// Use valid() function to check current
// iterator is valid entry or not
print($str->valid());

?>

<?php

// Create an empty SplObjectStorage
$gfg = new SplObjectStorage();

$obj1 = new StdClass;
$obj2 = new StdClass;
$obj3 = new StdClass;

$gfg[$obj1] = "GFG";
$gfg[$obj2] = "GeeksClasses";
$gfg[$obj3] = "SUDO";


// Use rewind function
$gfg->rewind();

while($gfg->valid()) {

    var_dump($gfg->getInfo());
    
    // Moving to next element
    $gfg->next();
}
?>