PHP Manual: Parse callbacks

Parse callbacks

Parse callables are invoked by yaml_parse(), yaml_parse_file() or yaml_parse_url() functions when a registered YAML tag is encountered. The callback is passed the tagged entity's value, the tag, and flags indicating the scalar entity style. The callback must return the data that the YAML parser should emit for this entity.

Example #1 Parse callback example

<?php
/**
 * Parsing callback for yaml tag.
 * @param mixed $value Data from yaml file
 * @param string $tag Tag that triggered callback
 * @param int $flags Scalar entity style (see YAML_*_SCALAR_STYLE)
 * @return mixed Value that YAML parser should emit for the given value
 */
function tag_callback ($value, $tag, $flags) {
  var_dump(func_get_args()); // debugging
  return "Hello {$value}";
}

$yaml = <<<YAML
greeting: !example/hello World
YAML;

$result = yaml_parse($yaml, 0, $ndocs, array(
    '!example/hello' => 'tag_callback',
  ));

var_dump($result);
?>

The above example will output something similar to:

array(3) {
  [0]=>
  string(5) "World"
  [1]=>
  string(14) "!example/hello"
  [2]=>
  int(1)
}
array(1) {
  ["greeting"]=>
  string(11) "Hello World"
}