<?php

define(

    'FLOAT',
	
    ';\s*?q=
    (1|0                            # 1 or 0
        (\.                         # Literal dot
            ([0-9]{1,2}[1-9]|       # One or Two Zeroes followed by 1...9 -OR-
             [0-9][1-9][0-9]?|      # Zero followed by 1...9, followed by an optional 0...9 -OR-
             [1-9]                  # 1...9 followed by:
                ([0-9]{0,2}|        # None and up to Two 0...9 -OR-
                 [0-9][1-9]|        # 0...9 and then followed by 1...9 -OR-
                 [1-9]{1,3}         # 1...9 once and up to three
                )
             )
        )?                          # All this is optional, and refers to float range
    )'
);

preg_match( sprintf( '@(?<params>%s)@x', FLOAT ), ';q=0.3444', $matches );

var_dump( $matches );