- print_r: documentation ( source)
- array_pad: documentation ( source)
<?php
$a=array("a"=>1,"b"=>1,"c"=>1,"e"=>1);
$b=array("a"=>5,"b"=>6,"c"=>7,"e"=>8);
print_r(array_pad(array(), 0, ""));
//print_r(array_combine(array_keys($a),array_values($b)));