<?php
 
$arrwords = array_flip(array(0=>'zero',1=>'one',2=>'two',3=>'three',4=>'four',5=>'five',6=>'six',7=>'seven',8=>'eight',9=>'nine'));
 
$s = "my long STRING with some Numbers 402three1345233 4023one345233";
 
$sanitised = array();    
foreach (explode(" ", $s) as $word) {
    $num = strtr(strtolower($word), $arrwords);
    $sanitised[] = is_numeric($num) ? str_repeat("*", strlen($word)) : $word;        
}
 
echo implode(" ", $sanitised);

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