[SOLVED] array_push (two arrays)

[malikah]

Why doesn't this work?:

 

$abc = array("a","b","c");
$def = array("d","e","f");

array_push($abc, $def);

echo $def[0];

// I THOUGHT THIS WOULD OUTPUT "a" BUT IT DOESN'T

[vineld]

Too quick.

[MatthewJ]

array_push() is pushing the $def array in as the 4th item of the $abc array

 

so to echo a would still be $abc[0] and to echo d would be $abc[3][0]

[malikah]

array_push() is pushing the $def array in as the 4th item of the $abc array

 

so to echo a would still be $abc[0] and to echo d would be $abc[3][0]

 

Thanks Matthew, that makes sense now. Do you know a speedy function for adding each element to the beginning of the second array?

[corbin]

array_merge

 

[malikah]

array_merge

 

 

Beautiful !

[Daniel0]

If you're looking for speedy insertion in the beginning you should look at another data structure than arrays such as a linked list. Putting something in the beginning of an array is by nature an expensive operation because you have to move all the other elements upwards.

 

See this quick benchmark for instance:

$iterations = 10000;

$start = microtime(true);
$array = array();
for ($i = 0; $i < $iterations; ++$i) {
array_unshift($array, $i);
}
echo 'Total time (array): ' . (microtime(true) - $start) . PHP_EOL;

unset($array);

$start = microtime(true);
$memory = memory_get_usage(true);
$list = new SplDoublyLinkedList();
for ($i = 0; $i < $iterations; ++$i) {
$list->unshift($i);
}
echo 'Total time (linked list): ' . (microtime(true) - $start) . PHP_EOL;

 

Total time (array): 6.3017320632935

Total time (linked list): 0.01022481918335

[vineld]

Yup but usually you wouldn't put elements at the start of an array. In this case I assume it's just about learning the basics of array functionality although I could be wrong.