for vs foreach vs while which is faster for iterating through arrays in php

Question

which one is the fastest for iterating through arrays in php? or does another exist which is also faster for iterating through arrays?

Answer 1

In general there is no applicable speed differences between the three functions.

To provide benchmark results to demonstrate the efficiency of varying methods used to iterate over an array from 1 to 10,000.

Benchmark results of varying PHP versions: https://3v4l.org/a3Jn4

while $i++: 0.00077605247497559 sec
for $i++: 0.00073003768920898 sec
foreach: 0.0004420280456543 sec
while current, next: 0.024288892745972 sec
while reset, next: 0.012929201126099 sec
do while next: 0.011449098587036  sec //added after terminal benchmark
while array_shift: 0.36452603340149 sec
while array_pop: 0.013902902603149 sec

Takes into consideration individual calls for count with while and for

$values = range(1, 10000);
$l = count($values);
$i = 0;
while($i<$l){
   $i++;
}

$l = count($values);
for($i=0;$i<$l;$i++){
}

foreach($values as $val){
}

---

The below examples using while, demonstrate how it would be used less efficiently during iteration.

When functionally iterating over an array and maintaining the current position; while becomes much less efficient, as next() and current() is called during the iteration.

while($val = current($values)){
    next($values);
}

If the current positioning of the array is not important, you can call reset() or current() prior to iteration.

$value = reset($values);
while ($value) {
    $value = next($values);
}

do ... while is an alternative syntax that can be used, also in conjunction with calling reset() or current() prior to iteration and by moving the next() call to the end of the iteration.

$value = current($values);
do{
}while($value = next($values));

array_shift can also be called during the iteration, but that negatively impacts performance greatly, due to array_shift re-indexing the array each time it is called.

while($values){
   array_shift($values);
}

Alternatively array_reverse can be called prior to iteration, in conjunction with calling array_pop. This will avoid the impact from re-indexing when calling array_shift.

$values = array_reverse($values);
while($values) {
   array_pop($values);
}

In conclusion, the speed of while, for, and foreach should not be the question, but rather what is done within them to maintain positioning of the array.

Terminal Tests run on PHP 5.6.20 x64 NTS CLI: