Working on picking up letters and digits in an array

[dreamkiller23]

<?php

function rev_arr($arr){
$cou=count($arr);
$returned_array=array();
for($i=$cou-1;$i>=0;$i--)
{
$returned_array[]=$arr[$i];
}
echo "$returned_array";
}

$b=array(21,6,12);
$e=rev_arr($b);
echo "$e";
?>

 

Okay so what i'm trying to do is to pickup an in string like

 

$instr= aBc35k5

 

my function will putput c3 and k5

 

 

i tried working the code in revers order but that doesn't seem to help me

in string can be any series of letter and digits

 

Please help!

 

[craygo]

Not really sure what you want to do here

 

What do the 21,6,12 mean???

[dreamkiller23]

no that's just a snippe of what i was working on. i want it to just print out the letter followed byt the number

[craygo]

so you want to only print out values where a letter is followed by a number?? Correct