Php check variable null
redefining local namespace constants will work 'I am not null!
Data range(0,max,1 start microtime(true for (x 0 ; x 100; x) sum sum(data, max end microtime(true echo "Time: ".(end - start)." sn Run times: # pass BY modified? .That's why #1 and #2 take similar times, whereas #3 takes 2 million times longer than #4.As used by exec ).Three useful functions for this are isset, empty and is_null.You do use array to tell the compiler "it is OK for the function to over-write my argument in place, I don't need the original any more." This can make a huge difference to performance when we have large amounts of memory to copy.If these functions are not used in correct way they can cause unexpected results.The caller should have it, at least as syntactic sugar."I'm done with the variable, it's OK to stomp on it in memory"?true var_dump nULL, null, null, null, Null, Null, false, false, false, false, False, False, true, true, true, true, True, True?
define false 'I am not global false!
Empty from, pHP Manual empty : empty Determine whether a variable is empty.
Time value no us 2 reference no us 3 valuue yes kerbal space program 0.25 mac s 4 reference yes.In other words, it will return true if the variable is an empty string, false, array null, 0?, 0, and an unset variable.Otherwise it leads to unreadable code: because the person reading the function call doesn't expect it to pass by reference.Value of variable (var) isset(var) empty(var) is_null(var) (an empty string) bool(true) bool(true) (space) bool(true false bool(true) bool(true) true bool(true) array (an empty array) bool(true) bool(true) null bool(true) bool(true) 0 (0 as a string) bool(true) bool(true) 0 (0 as an integer) bool(true) bool(true).0 (0.PHP doesn't allow it, but it would be meaningful for the caller to decide to pass data in as a reference.All these function return a boolean value.In this post I will explain the differences between these functions.(This is the only way it is done in C, arrays are always passed as pointers).