1.2.842. No array_merge() In Loops¶
array_merge() is memory intensive : every call will duplicate the arguments in memory, before merging them.
To handle arrays that may be quite big, it is recommended to avoid using array_merge() in a loop. Instead, one should use array_merge() with as many arguments as possible, making the merge a on time call. Note that array_merge_recursive() and file_put_contents() are affected and reported the same way.
<?php
// A large multidimensional array
$source = ['a' => ['a', 'b', /*...*/],
'b' => ['b', 'c', 'd', /*...*/],
/*...*/
];
// Faster way
$b = array();
foreach($source as $key => $values) {
//Collect in an array
$b[] = $values;
}
// One call to array_merge
$b = call_user_func_array('array_merge', $b);
// or with variadic
$b = call_user_func('array_merge', ..$b);
// Fastest way (with above example, without checking nor data pulling)
$b = call_user_func_array('array_merge', array_values($source))
// or
$b = call_user_func('array_merge', ...array_values($source))
// Slow way to merge it all
$b = array();
foreach($source as $key => $values) {
$b = array_merge($b, $values);
}
?>
See also Speed up array_merge().
1.2.842.1. Suggestions¶
Store all intermediate arrays in a temporary variable, and use array_merge() once, with ellipsis or call_user_func_array().
1.2.842.2. Specs¶
Short name |
Performances/ArrayMergeInLoops |
Rulesets |
All, Analyze, CE, CI-checks, Changed Behavior, Performances, Top10 |
Exakat since |
0.8.4 |
PHP Version |
All |
Severity |
Major |
Time To Fix |
Quick (30 mins) |
Precision |
High |
ClearPHP |
|
Examples |
|
Available in |