$re = '~^\h*\[if.*\]\R # if in the first line
(?<if>(?:(?!\[elseif)[\s\S])+)\R # output
^\h*\[elseif.*\]\R # elseif
(?<elseif>(?:(?!\[else)[\s\S])+)\R # output
^\h*\[else.*\]\R # elseif
(?<else>(?:(?!\[endif)[\s\S])+)\R # output
^\[endif\]
~mx';
$str = '[if:(a+b-c/d*e)|(x-y)&!(z%3=0)]
output
[elseif:(\'b\'+\'atman\'=\'batman\')]
output2
out as well
[else]
output3
some other output here
[endif]';
preg_match_all($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