- var_dump: documentation ( source)
- array_combine: documentation ( source)
- preg_match_all: documentation ( source)
<?php
$data = 'BUTTONSOURCE[18]=AngellEYE_PHPClass&VERBOSITY[4]=HIGH&USER[6]=tester¶m1=value1&<param2>=value2!';
preg_match_all('/([^=&]+)\=([^=&]+)/', $data, $result);
$result = array_combine($result[1], $result[2]);
var_dump($result);