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Can you please explain the difference between accessing a class method via -> and via ::

:: is allowed to access methods that can perform static operations, i.e. those, which do not require object initialization.

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How come code <?php print "Contents: $arr[1]"; ?> works, but <?php print "Contents: $arr[1][2]"; ?> doesn't for two-dimensional array of mine?	If the variable $a is equal to 5 and variable $b is equal to character a, what's the value of $$b?