- var_dump: documentation ( source)
- preg_match: documentation ( source)
<?php
$str1 = "Preved kagdila? segodnya v 12:30";
$str2 = "Preved 2132944321";
$str3 = "123-343-123 spice 2934-439-944 it sk";
$pattern = '(([1-9]+)([0-9]{6,8}))';
var_dump(preg_match($pattern, $str1));
var_dump(preg_match($pattern, $str2));
var_dump(preg_match($pattern, $str3));