The example code given for FormattableMarkup::placeholderFormat() contains typos and syntax errors

On FormattableMarkup::placeholderFormat(), the secure examples are the following.

$this->placeholderFormat('<a href=":foo">link text</a>, ['@foo' => $some_variable]);
$this->placeholderFormat('<a href=":foo" title="static text">link text</a>, ['@foo' => $some_variable]);
$this->placeholderFormat('<a href=":foo">@foo</a>, ['@foo' => $some_variable]);
// Use : placeholder inside an HTML tag.
$this->placeholderFormat('<img src=":foo" />, ['@foo' => '/image.png']);

The placeholders used in the strings are different from the placeholders in the array passed as second argument. For example, the first example uses :foo as placeholder, but the array contains '@foo'. Furthermore, the literal strings passed as first argument do not include string delimiters.

The correct examples are the following one.

$this->placeholderFormat('<a href=":foo">link text</a>', [':foo' => $some_variable]);
$this->placeholderFormat('<a href=":foo" title="static text">link text</a>', [':foo' => $some_variable]);
$this->placeholderFormat('<a href=":foo">@foo</a>', [':foo' => $some_variable]);
// Use : placeholder inside an HTML tag.
$this->placeholderFormat('<img src=":foo" />', [':foo' => '/image.png']);