$re = '/".*?(?<!\\\\)"(*SKIP)(*F)| +/m';
$str = 'key1=value1 key1=value1 spaces="some spaces in text" nested1="key2=value2 key2=value2 key2=value2" nested2= "key2=value2, key2=value2, key2=value2" quoted="his name is \\"no body\\"" something=else';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php