I just noticed that iterating an array using a while and array_shift behaves differently from a simple for loop when encounters an empty string. Here's a sample:
While loop:
$arr=[1, "",1,""];
while ($elm = array_shift($arr))
{
var_dump($elm);
}
For loop:
$arr=[1, "",1,""];
for ($i = 0; $i<count($arr); $i++)
{
var_dump($arr[$i]);
}
die();
Why does the while exit the loop?
Because an empty string is a falsy value in PHP:
var_dump((bool) ""); // bool(false)
To make the first example work with empty strings you should check against array_shift returning NULL:
$arr = [1, "", 1, ""];
while (($elm = array_shift($arr)) !== NULL) {
var_dump($elm);
}
Explanation
array_shift removes the first element from the array and returns its value:
$arr = [1, ""];
array_shift($arr); // we get 1
array_shift($arr); // we get ""
array_shift($arr); // we get NULL because the array is empty now
In your first example you have while ($elm = array_shift($arr)) which means:
$elm$elm as a boolean (this is done implicitly) and only continue if it evaluates to TRUE.Let's manually go through each iteration to make it more clear:
first iteration: while ($elm = 1) -> while (true) because 1 is truthy. We continue the loop.
second iteration: while ($elm = "") -> while (false) because an empty string is falsy. We exit the loop.
$elm = array_shift($arr) is equivalent to $elm = "" which is evaluated by the left-side variable value set in the operation, e.g., "", which evaluates to falsey.
array_shift changes the original array (which takes additional time), the for loop doesn't: $arr = [1,2,3]; array_shift($arr);array_shift($arr);array_shift($arr); var_dump($arr); outputs an empty array.Because the empty string evaluates to false
Because the second value of your array is empty string which converts to bool false
Try to use another array and everything will be good:
$arr=[1, "non-empty value", 1, "another non-empty value"];
while ($elm = array_shift($arr))
{
var_dump($elm);
echo '<br>'; // this is bonus ;)
}
The solutions proposed by others are still prone to error if an array contains a null. If it's really necessary to modify the array rather than do a simple foreach, a robust way to construct this would be:
while ($arr)
{
$elm = array_shift($arr)
var_dump($elm);
}
This is because arrays are always truthy unless they're empty, regardless of what values they contain.
truevalue inwhile(). In first array, you second value isnull, Which consider asfalseOR0value. Hence while loop getting stop.