Is it faster to declare array before using the array php?
For example, is it faster to declare an array and then set a value:
$arr = [];
$arr['foo'] = 'bar';
Or just jump right into setting a value without declaring the object first:
$arr['foo'] = 'bar';
Please note, I do not want to do the following:
$arr = ['foo' => 'bar'];
I always declare because I don't want to run into undefined vars errors. But I was curious as well. Let's test!
$size = 1000000;
$start_time = microtime(true);
for($i=1;$i<=$size;$i++):
$arr = [];
$arr['foo']='bar';
unset($arr);
endfor;
$results['declare first'] =
floor((microtime(true)-$start_time) * 1000).' milliseconds';
unset($arr, $i, $start_time);
$start_time = microtime(true);
for($i=1;$i<=$size;$i++):
$arr['foo']='bar';
unset($arr);
endfor;
$results['do not declare'] =
floor((microtime(true)-$start_time) * 1000).' milliseconds';
print_r($results);
Typical result on my PC: PHP 5.6.23 on Win 7 x64:
[
'declare first' => '464 milliseconds',
'do not declare' => '376 milliseconds',
]
A 100-millisecond difference after 1 million ops means you basically won't notice the difference unless you have several million arrays. So declare first :-)
for(): and endfor, I have always just done for {}
for...endfor, if...endif, foreach...endforeach and while...endwhile. Makes code easier to read for me than have just a closing bracketWhile there is a speed benefit to not declaring (see BeetleJuice's answer), there is a big potential downside:
If you don't declare a new array, and the data that creates / updates the array fails for any reason, then any future code that tries to use the array will E_FATAL because the array doesn't exist.
quoted from: Is it necessary to declare PHP array before adding values with []?
If you don't declare a new array, and the data that creates / updates the array fails for any reason, then any future code that tries to use the array will E_FATAL because the array doesn't exist.
For example, foreach() will throw an error if the array was not declared and no values were added to it. However, no errors will occur if the array is simply empty, as would be the case had you declared it.
