How to get only the number from a string?

Question

I have strings like this:

Lesson 001: Complete

I want to only get the number part, in this case 001.

I tried this:

  $str = the_title();
  preg_match_all('!\d+!', $str, $matches);
  $number = implode(' ', $matches[0]);
  echo $number;

But echo $number outputs the entire string once again: Lesson 001: Complete

How to do this correctly?

As I said to @ʰᵈˑ For some reason works if I do `$s = "Lesson 001: Complete";` but not when I do `$s = the_title();` Even though their ouput is the same. Not sure why. — alexchenco, Apr 08 '15 at 10:08
@alexchenco Let me guess do: `var_dump(the_title());` and you will get `NULL`, right? You know why? [Because the function prints this, but doesn't return it!](https://codex.wordpress.org/Function_Reference/the_title) **Solution ? use: get_the_title()** (100 points for me :)?) — Rizier123, Apr 08 '15 at 10:09

score 19 · Accepted Answer · answered Apr 08 '15 at 09:57

19

You can use filter_var and sanitize the string to only include integers.

$s = "Lesson 001: Complete";
echo filter_var($s, FILTER_SANITIZE_NUMBER_INT);

You can use a regular expression to match only integers.

$s = "Lesson 001: Complete";
preg_match("/([0-9]+)/", $s, $matches);
echo $matches[1];

answered Apr 08 '15 at 09:57

ʰᵈˑ

For some reason works if I do `$s = "Lesson 001: Complete";` but not when I do `$s = the_title();` Even though their ouput is the same. Weird. – alexchenco Apr 08 '15 at 10:07
1

@alexchenco see http://stackoverflow.com/questions/29511413/how-to-get-only-the-number-from-a-string/29511466#comment47179172_29511413 (Rizier123 gets 100pts) – ʰᵈˑ Apr 08 '15 at 10:15
Note: FILTER_SANITIZE_NUMBER_INT - removes all characters *except* digits, plus and minus sign. – Leon Jun 18 '22 at 13:45

score 2 · Answer 2 · answered Apr 08 '15 at 09:58

2

you can try with /\d+/

$str = the_title();
preg_match_all('/\d+/', $str, $matches);
echo $matches[0];

answered Apr 08 '15 at 09:58

Naing Lin Aung

2 Answers2