如果包含数字0到9和字符a到z，我该如何检查变量？ [重复]

I would like to know how can I check if a variable contains numbers 0 to 9 and characters a to z, like that:

 if($string contains numbers[0-9] and characters[a-z])
 {
  echo "true";
} else {echo "false";}

</div>

You can use regex. preg_match

$str = "aab1230";
if(preg_match('/^[0-9a-z]+$/', $str)) {
   // contains only characters [0-9] and/or [a-z]
}