I have two arrays in PHP as follows:
People:
Array
(
[0] => 3
[1] => 20
)
Wanted Criminals:
Array
(
[0] => 2
[1] => 4
[2] => 8
[3] => 11
[4] => 12
[5] => 13
[6] => 14
[7] => 15
[8] => 16
[9] => 17
[10] => 18
[11] => 19
[12] => 20
)
How do I check if any of the People elements are in the Wanted Criminals array?
In this example, it should return true because 20 is in Wanted Criminals.
There's little wrong with using array_intersect() and count() (instead of empty).
For example:
$bFound = (count(array_intersect($criminals, $people))) ? true : false;
Performance test for in_array vs array_intersect:
$a1 = array(2,4,8,11,12,13,14,15,16,17,18,19,20);
$a2 = array(3,20);
$intersect_times = array();
$in_array_times = array();
for($j = 0; $j < 10; $j++)
{
/***** TEST ONE array_intersect *******/
$t = microtime(true);
for($i = 0; $i < 100000; $i++)
{
$x = array_intersect($a1,$a2);
$x = empty($x);
}
$intersect_times[] = microtime(true) - $t;
/***** TEST TWO in_array *******/
$t2 = microtime(true);
for($i = 0; $i < 100000; $i++)
{
$x = false;
foreach($a2 as $v){
if(in_array($v,$a1))
{
$x = true;
break;
}
}
}
$in_array_times[] = microtime(true) - $t2;
}
echo '<hr><br>'.implode('<br>',$intersect_times).'<br>array_intersect avg: '.(array_sum($intersect_times) / count($intersect_times));
echo '<hr><br>'.implode('<br>',$in_array_times).'<br>in_array avg: '.(array_sum($in_array_times) / count($in_array_times));
exit;
Here are the results:
0.26520013809204
0.15600109100342
0.15599989891052
0.15599989891052
0.1560001373291
0.1560001373291
0.15599989891052
0.15599989891052
0.15599989891052
0.1560001373291
array_intersect avg: 0.16692011356354
0.015599966049194
0.031199932098389
0.031200170516968
0.031199932098389
0.031200885772705
0.031199932098389
0.031200170516968
0.031201124191284
0.031199932098389
0.031199932098389
in_array avg: 0.029640197753906
in_array is at least 5 times faster. Note that we "break" as soon as a result is found.
if 'empty' is not the best choice, what about this:
if (array_intersect($people, $criminals)) {...} //when found
or
if (!array_intersect($people, $criminals)) {...} //when not found
You could also use in_array as follows:
<?php
$found = null;
$people = array(3,20,2);
$criminals = array( 2, 4, 8, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20);
foreach($people as $num) {
if (in_array($num,$criminals)) {
$found[$num] = true;
}
}
var_dump($found);
// array(2) { [20]=> bool(true) [2]=> bool(true) }
While array_intersect is certainly more convenient to use, it turns out that its not really superior in terms of performance. I created this script too:
<?php
$found = null;
$people = array(3,20,2);
$criminals = array( 2, 4, 8, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20);
$fastfind = array_intersect($people,$criminals);
var_dump($fastfind);
// array(2) { [1]=> int(20) [2]=> int(2) }
Then, I ran both snippets respectively at: http://3v4l.org/WGhO7/perf#tabs and http://3v4l.org/g1Hnu/perf#tabs and checked the performance of each. The interesting thing is that the total CPU time, i.e. user time + system time is the same for PHP5.6 and the memory also is the same. The total CPU time under PHP5.4 is less for in_array than array_intersect, albeit marginally so.
Here's a way I am doing it after researching it for a while. I wanted to make a Laravel API endpoint that checks if a field is "in use", so the important information is: 1) which DB table? 2) what DB column? and 3) is there a value in that column that matches the search terms?
Knowing this, we can construct our associative array:
$SEARCHABLE_TABLE_COLUMNS = [
'users' => [ 'email' ],
];
Then, we can set our values that we will check:
$table = 'users';
$column = 'email';
$value = '[email protected]';
Then, we can use array_key_exists() and in_array() with eachother to execute a one, two step combo and then act upon the truthy condition:
// step 1: check if 'users' exists as a key in `$SEARCHABLE_TABLE_COLUMNS`
if (array_key_exists($table, $SEARCHABLE_TABLE_COLUMNS)) {
// step 2: check if 'email' is in the array: $SEARCHABLE_TABLE_COLUMNS[$table]
if (in_array($column, $SEARCHABLE_TABLE_COLUMNS[$table])) {
// if table and column are allowed, return Boolean if value already exists
// this will either return the first matching record or null
$exists = DB::table($table)->where($column, '=', $value)->first();
if ($exists) return response()->json([ 'in_use' => true ], 200);
return response()->json([ 'in_use' => false ], 200);
}
// if $column isn't in $SEARCHABLE_TABLE_COLUMNS[$table],
// then we need to tell the user we can't proceed with their request
return response()->json([ 'error' => 'Illegal column name: '.$column ], 400);
}
// if $table isn't a key in $SEARCHABLE_TABLE_COLUMNS,
// then we need to tell the user we can't proceed with their request
return response()->json([ 'error' => 'Illegal table name: '.$table ], 400);
I apologize for the Laravel-specific PHP code, but I will leave it because I think you can read it as pseudo-code. The important part is the two if statements that are executed synchronously.
array_key_exists()andin_array()are PHP functions.
source:
The nice thing about the algorithm that I showed above is that you can make a REST endpoint such as GET /in-use/{table}/{column}/{value} (where table, column, and value are variables).
You could have:
$SEARCHABLE_TABLE_COLUMNS = [
'accounts' => [ 'account_name', 'phone', 'business_email' ],
'users' => [ 'email' ],
];
and then you could make GET requests such as:
GET /in-use/accounts/account_name/Bob's Drywall (you may need to uri encode the last part, but usually not)
GET /in-use/accounts/phone/888-555-1337
GET /in-use/users/email/[email protected]
Notice also that no one can do:
GET /in-use/users/password/dogmeat1337 because password is not listed in your list of allowed columns for user.
Good luck on your journey.
That code is invalid as you can only pass variables into language constructs. empty() is a language construct.
You have to do this in two lines:
$result = array_intersect($people, $criminals);
$result = !empty($result);
Source: Stackoverflow.com