Insert different strings before and after variable in PHP
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I have 4 PHP variables, each variable consists of dynamic checkboxes, sometimes it can be one variable sometimes more but not more than 4:

    $type = 'type_id = 2';
    $color = 'color_id = 3';
    $man = 'man_id = 5';
    $size = 'size_id = 4 or size_id = 5';

I need to form of these variables Mysql query, the problem is how to add WHERE and AND strings before each variable. In front of first variable I need to add WHERE (it can be $type or $color or other). If first variable is active and other is checked I need to add AND to form proper query. e.g

if checked only "type" checkboxes:

    WHERE $type

if checked "size" and "type" checkboxes:

    WHERE $size AND $type

and so on... Hope you understand my problem, sorry for bad english.