- array_combine: documentation ( source)
- print_r: documentation ( source)
- preg_match_all: documentation ( source)
<?php
$re = '/([\D]+)|([\d]+)/';
$str = 'a74b8c0d3845e7';
preg_match_all($re, $str, $matches);
print_r(array_combine($matches[1],$matches[2]));