PHP Large Size Array
30 Nov 2014
In PHP, we use arrays lots of times and every our projects. In this article, I will try to handle some operations for large size array. For example, we can use in_array method to check if a value exists in an array.
$some_values = array(1, 2, 3, 4, 5);
var_dump(in_array(1, $some_values));
// bool(true)
The result is clear. $some_values array has “1” element as a value. Sometimes we must check all the array to compare each other. For example, we have a number list in an array and we try to check singularity of all elements.
First Example:
$some_values = array(1, 2, 3, 3, 4, 5);
$temporary_values = array();
for ($i = 0; $i < count($some_values); $i++) {
$found = false;
for ($j = 0; $j < count($temporary_values); $j++) {
if ($temporary_values[$j] == $some_values[$i]) {
$found = true;
break;
}
}
if (!$found) {
// Checking or processing some other things
$temporary_values[] = $some_values[i];
}
}
print_r($temporary_values); // All elements of array is singular
Second Example:
$some_values = array(1, 2, 3, 4, 5);
$temporary_values = array();
for ($i = 0; $i < count($some_values); $i++) {
if (!in_array($some_values[$i], $temporary_values)) {
// Checking or processing some other things
$temporary_values[] = $some_values[$i];
}
}
print_r($temporary_values); // All elements of array is singular
In two example, run time is the same and they are O(n2) complexity in worst case. You can check in_array method to understand why they are the same. in_array method use php_search_array method directly. And they have a loop to move on array.
If we have some small array, in_array function save our time. Do we have large size array? If we have an array and it has 10,000+ elements. In this time, php return us some errors like that:
Fatal error: Maximum execution time of 30 seconds exceeded in .... on line 4
Because, our application execution time is more than our php configs. There are two solution for that. First one is change your max_execution_time from your php.ini file. Second one is change your application.
I will try to explain how we can change our application for this spesific problem. Firstly, we will get rid of inner loop.
$some_values = array("a1", "a2", "a3", "a4", "a5", ..., "a999999", "a1000000");
$temporary_array = array();
for ($i = 0; $i < count($some_values); $i++) {
$temporary_array[$some_values[$i]] = $i;
}
$temporary_values = array();
foreach ($temporary_array as $key => $value) {
$temporary_values[] = $key;
}
print_r($temporary_values); // All elements of array is singular
To minimize out code, we can use some php standart function. Firstly, we use array_flip to create temporary_array.
$some_values = array("a1", "a2", "a3", "a4", "a5", ..., "a999999", "a1000000");
$temporary_array = array_flip($some_values);
$temporary_values = array();
foreach ($temporary_array as $key => $value) {
$temporary_values[] = $key;
}
print_r($temporary_values); // All elements of array is singular
Try to use array_keys to get keys of temporary_array.
$some_values = array("a1", "a2", "a3", "a4", "a5", ..., "a999999", "a1000000");
$temporary_array = array_flip($some_values);
$temporary_values = array_keys($temporary_array);
print_r($temporary_values); // All elements of array is singular
Now remove some unused variables from our code.
$some_values = array("a1", "a2", "a3", "a4", "a5", ..., "a999999", "a1000000");
$temporary_values = array_keys(array_flip($some_values));
print_r($temporary_values);
Thank you
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