You can combine this value by xoring it with other values such as time(), (int)microtime(), ip2long($_SERVER, $_SERVER, getmypid().
R round date up to nearest integer free#
Then $r can be used as a good entropy source, if the free space in your temporary folder used by PHP is constantly evolving within a large range of values. Useful also to reduce an arbitrarily large floating point value into an entropy source, by first transforming this value into a pair using logarithm functions with distinct bases (add 1 if the function can return 0, to avoid floating point errors with logarithms!):
Very useful with trigonometric functions to reduce the angle argument to a circle that includes angle 0.
Mathematical functions lack a floating point version of the modulo operation, which returns the difference between the floor() of the argument and the argument itself: THe moral of this story - never use float for anything that needs to be accurate! If you're doing prices for products or a shopping cart, then always use an integer and store prices as a number of pence, you'll thank me for this later :) When the 79.99 was multiplied by 100, the actual value stored in the float was probably something like 7998.9999999999999999999999999999999999, PHP would print out 7999 when the value is displayed but floor would therefore round this down to 7998. The thing to remember here is that the way a float stores a value makes it very easy for these kind of things to happen. Here's a baffling example of how floor can be tripped up by this:
R round date up to nearest integer archive#
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