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    <p>You could use a <a href="http://en.wikipedia.org/wiki/Mask_(computing)" rel="nofollow noreferrer">bitmask</a>.</p> <p>If all your permissions are (or can be generalised to) a set of yes/no conditions, it's quite easy.</p> <p>In your example, you have Create, Read, Update and Delete. That's 4 bits, so you need a 4-bit number to store permissions. (0000 to 1111 in binary = 0 to 15 in decimal)</p> <p>Someone who can only read would have permissions 0100 (4 in decimal), and someone who can create/read/update would have persmissions 1110 (14 in decimal). Administrators who have full access would have persmissions 1111 (15 in decimal).</p> <p>The way you would check these in PHP would be with the bitwise OR operator <code>|</code>.</p> <p>For example</p> <pre><code>// you could write a function getUserPermission($strUsername) // which returns a permission number, say 10 (1010 in binary) // which means he/she can create/update but not read/delete $userPermissions = getUserPermission("TedWong"); $permissionCreate = 8; // 1000; $permissionRead = 4; // 0100; $permissionUpdate = 2; // 0010; $permissionDelete = 1; // 0001; if ($userPermissions | $permissionCreate) { //user has permission to create } if ($userPermissions | $permissionRead) { //User has permission to read } if (!($userPermissions | $permissionDelete)) { //User doesn't have permission to delete } if ($userPermissions | $permissionUpdate &amp;&amp; $userPermissions | $permissionCreate) { //User has permission to create and update. } </code></pre> <p>If you want more permissions, you just need to introduce more bits.</p> <p>As for your update all posts/delete own posts in your example, I would have a 5-bit permission structure: Create, Read, Delete, UpdateOwn, UpdateAll.</p> <p>You can have many permissions, but would be limited by the data structure storing them. For example, if you are storing the permission mask in a 32-bit integer, then you can only have up to 32 permissions.</p> <p>here is a full list of 4-bit permissions for your example:</p> <pre><code>0000 // 0: No Permissions 0001 // 1: Delete 0010 // 2: Update 0011 // 3: Delete + Update 0100 // 4: Read 0101 // 5: Read + Delete 0110 // 6: Read + Update 0111 // 7: Read + Delete + Update 1000 // 8: Create 1001 // 9: Create + Delete 1010 // 10: Create + Update 1011 // 11: Create + Delete + Update 1100 // 12: Create + Read 1101 // 13: Create + Read + Delete 1110 // 14: Create + Read + Update 1111 // 15: Create + Read + Delete + Update </code></pre> <p>So that means the <i>INTEGER</i> <b>6</b> (which in <i>BINARY</i> is equal to <b>0110</b>) gives permissions Read/Update but not Create/Delete. In the same way each <i>integer</i> has a set of permissions associated with it. You can store up to as many permissions in the integer as many bits there are that represent that integer (usually 32).</p> <p>So you can see that with a 4-bit integer (decimal numbers 0 to 15) can give you 4 yes/no permissions. If you use a 32-but integer then you can have up to 32 yes/no permissions.</p> <p>Check the <a href="http://php.net/manual/en/language.types.integer.php" rel="nofollow noreferrer">PHP documentation</a> on how to determine the maximum size of your integers. (It depends on the platform you're running your PHP parser on). I think generally speaking a 32-bit system/OS will allow for 32-bit integers, and 64-bit system/OS will allow for 64-bit integers.</p> <p>Check <a href="https://stackoverflow.com/search?q=php+bitmask+permissions">these other threads</a> on SO for discussions on pros/cons of using bitmasks vs other methods.</p>
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    1. POHow to represent user rights in a elegant way?
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    1. POHow to represent user rights in a elegant way?
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    1. COI see, but how many permission I can have? I see that is multiple in next permission, will it become a super big int? if I have the right of read and update ONLY, and my permission is 6, right?
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    2. CONo, if you have 4 permissions then you have a 4-bit bitmask = 0-15. If you have 5 permissions then you have 0-31. 6 permissions = 0-63, etc. In the example you gave, each user will have a decimal permission number between 0 and 15 only. 0 means no permission, 15 means all permissions.
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    3. COwhy it is not 6? read is 4, and update is 2...I have these two, why it is not 6?
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