Historical Results
Based on (2) saved test runs, The test labeled "$k => $dummy" was (on average) the faster by 0.0119 seconds, (1.174% faster)
The $k => $dummy test took 1.0051 seconds.
The array_keys() test took 1.017 seconds.
Nitty-Gritty
Each test case ran 20 random code order iterations consisting of 260,224 loops for a total of 5,204,480 runs.
- Line execution difference (0.000002) milliseconds.
- Avg difference (0.000) milliseconds per 260,224 loops.
- Total difference 11.94 milliseconds for 5,204,480 loops
The iteration variablity for Code 1 was (0.0000) milliseconds and Code 2 was (0.0000) milliseconds. The lower and the closer together there values are the more accurate the results are.
Code
The first test, "$k => $dummy", was:
foreach ($GLOBALS['dummy'] as $k => $dummy) $k + 1;
The second test, "array_keys()", was:
foreach (array_keys($GLOBALS['dummy']) as $k) $k + 1;