$re = '/([A-Z][a-zA-Z0-9]*)\s*=\s*(.*?)(?=,[A-Z]|$)/';
$str = 'Variable1=somevalue1,Variable2=so,me,value2,Variable3=some,value2,Variable4 = Hello, Wor,ld,d,ThisVariable=ThisOneWill,Fail,Hello=wo, rld';
preg_match_all($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