Smartest way to extract a string number and convert in to int - php

Question

I need to create a function which will be able to extract string representations of numbers and return them as integers but I'm unsure about the most efficient way to do this.
I was thinking that I could possibly have a dictionary of numbers and look for matches in the string.
Or I could trim away anything that came before the word "third" and after the word "ninth" and process the results.
string
"What is the third, fifth, sixth and ninth characters to question A"
desired output
array(3,5,6,9);

Answer 1

Rather ugly code (because of "global"), but simply working
$dict = array('third' => 3, 'fifth' => 5, 'sixth' => 6, 'ninth' => 9);
$string = 'What is the third, fifth, sixth and ninth characters to question A';
$output = null;
if (preg_match_all('/(' . implode('|', array_keys($dict)) . ')/', $string, $output))
$output = array_map(function ($in) { global $dict; return $dict[$in]; }, $output[1]);
print_r($output);
Update
The exact code without use of "global":
$dict = array('third' => 3, 'fifth' => 5, 'sixth' => 6, 'ninth' => 9);
$string = 'What is the third, fifth, sixth and ninth characters to question A';
$output = null;
if (preg_match_all('/(' . implode('|', array_keys($dict)) . ')/', $string, $output))
$output = array_map(function ($in) use ($dict) { return $dict[$in]; }, $output[1]);
print_r($output);

Answer 2

See this, complete work for you!
<?php
function get_numbers($s) {
$str2num = array(
'first' => 1,
'second' => 2,
'third' => 3,
'fourth' => 4,
'fifth' => 5,
'sixth' => 6,
'seventh' => 7,
'eighth' => 8,
'ninth' => 9,
);
$pattern = "/(".implode(array_keys($str2num), '|').")/";
preg_match_all($pattern, $s, $matches);
$ans = array();
foreach($matches[1] as $key) {
array_push($ans, $str2num[$key]);
}
return $ans;
}
var_dump(get_numbers("What is the third, fifth, sixth and ninth characters to question A"));

Answer 3

$string = "What is the first, third, first, first, third, sixth and ninth characters to question A";
$numbers = array('first' => 1, 'second' => 2, 'third' => 3); //...
preg_match_all("(".implode('|',array_keys($numbers)).")", $string, $matches );
$result = array();
foreach($matches[0] as $match){
$result[] = $numbers[$match];
}
var_dump($result);