如何从存储在方法/函数中的字符串值中取整数？

In buddypress plugin subject is printed using this code

<?php bp_the_thread_subject(); ?>

at my end this function/method is printing result like Hello world: 1236 . I want to take only integer value from this. But when i am applying anything to this function/method, it is getting zero result. How to do that ?

You can use the filter_var function to extract the number

<?php
    function bp_the_thread_subject(){
        //All your logic to return the string....

        return 'Hello world: 1236';
    }

    $value = filter_var(bp_the_thread_subject(), FILTER_SANITIZE_NUMBER_INT);

    echo $value // 1236;
?>

Assuming that bp_the_thread_subject() returns Hello world: 1236, when can use filter_var with FILTER_SANITIZE_NUMBER_INT to remove everything that's not an int.

$identity  = filter_var( bp_the_thread_subject(), FILTER_SANITIZE_NUMBER_INT );
$myInt = (int)$identity;
var_dump($myInt);
//int(1236)

Ideone Demo

You can use preg_match to return only the number:

<?php preg_match('/\d+/', bp_the_thread_subject(), $matches)[1] ?>