The libxml_set_external_entity_loader of libxml for PHP changes the default external entity loader.

Syntax

libxml_set_external_entity_loader(
    ?callable $resolver_function
): bool

Parameters

resolver_function

A callable with the following signature:

resolver(
    ?string $public_id,
    string $system_id,
    array $context
): resource|string|null

public_id

The public ID.

system_id

The system ID.

context

An array with the four elements "directory", "intSubName", "extSubURI" and "extSubSystem".

This callable should return a resource, a string from which a resource can be opened. If null is returned, the entity reference resolution will fail.

Return

Returns true on success or false on failure.

Examples

1 · resolver_function

<?

function resolver($public_id, $system_id, $context)
{
    return "mystring";
}

$resolver_function = "resolver";

$return = libxml_set_external_entity_loader($resolver_function);

var_export($return);

true

2 · DOMDocument

<?

function resolver($public_id, $system_id, $context)
{
    var_dump($public_id, $system_id, $context);

    return "mystring";
}

$resolver_function = "resolver";

libxml_set_external_entity_loader($resolver_function);

$source =
<<<XML
<!DOCTYPE mytopelement PUBLIC "myregistration//myorganization//mytype mylabel mydefinition//mylanguage" "https://mydomain.com/mypath">
<my-element></my-element>
XML;

$dom = new DOMDocument;
$dom->loadXML($source);
$dom->validate();

<!doctype html>
<html>
<head>
    <title>PHP</title>
    <style>
        html, a
        {
            background-color: rgb(255 0 255 / 0.1);
        }
        a
        {
            color: purple;
            transition-duration: 1s;

            &:hover
            {
                background-color: rgb(0 0 0 / 0.1);
                color: black;
                text-decoration-color: transparent;
            }
        }
    </style>
</head>
<body>
    <a href="/php/">PHP</a>
    <script>
        function myfunction(myparameter)
        {
            const mytarget = myparameter.target;
            const mystyle = mytarget.style;
            mystyle.position = "absolute";
            if(mystyle.left == "")
            {
                mystyle.left = "8px";
                mystyle.top = "8px";
            }
            mystyle.left = `${Math.random() * (window.innerWidth - mytarget.offsetWidth)}px`;
            mystyle.top = `${Math.random() * (window.innerHeight - mytarget.offsetHeight)}px`;
        }
        document.querySelector("a").addEventListener("mouseout", myfunction);
    </script>
</body>
</html>