Php obtains the number Regular Expression in the string.

 

The filter_sanitize_number_int filter deletes all invalid characters in the number.

This filter allows all numbers and + -.
*/

$ Number = "5-2 + 3 pp ";

Var_dump (filter_var ($ number, filter_sanitize_number_int ));

/*
Verification number: ^ [0-9] * $
Verify the n-digit number: ^ d {n} $
Verify the number of at least n digits: ^ d {n,} $
Verify m-n digits: ^ d {m, n} $
Verify the number starting with zero or zero: ^ (0 | [1-9] [0-9] *) $
Verify the positive number of two decimal places: ^ [0-9] + (. [0-9] {2 })? $
Verify the positive number of 1-3 decimal places: ^ [0-9] + (. [0-9] {1, 3 })? $
Verify a non-zero positive integer: ^ +? [1-9] [0-9] * $
Verify a non-zero negative integer: ^-[1-9] [0-9] * $
Verify non-negative integer (positive integer + 0) ^ d + $
Verify non-positive integer (negative integer + 0) ^ (-d +) | (0 +) $
3 characters for verification: ^. {3} $

For more details, see: http://www.bkjia.com/phper/php-function/35065.htm
*/