Code:
code

$myVar='xy12 d2_6 dkr';

$myvar=$str_replace('0','', $myVar);
$myvar=$str_replace('1','', $myVar);
$myvar=$str_replace('2','', $myVar);
$myvar=$str_replace('3','', $myVar);
$myvar=$str_replace('4','', $myVar);
$myvar=$str_replace('5','', $myVar);
$myvar=$str_replace('6','', $myVar);
$myvar=$str_replace('7','', $myVar);
$myvar=$str_replace('8','', $myVar);
$myvar=$str_replace('9','', $myVar);

echo $myVar;

result

xy d_ dkr
The code above removes all numbers of the variable '$myVar',
I guess there may be better code for it.
Do you have any?
Maybe regular expression...