Checking to see if one array s elements are in another array in PHP

Question

I have two arrays in PHP as follows   People   Array        0    gt  3      1    gt  20     Wanted Criminals   Array        0    gt  2      1    gt  4      2    gt  8      3    gt  11      4    gt  12      5    gt  13      6    gt  14      7    gt  15      8    gt  16      9    gt  17      10    gt  18      11    gt  19      12    gt  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

User · Answer

You could also use in array as follows    lt  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   gt  bool true     2   gt  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    lt  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   gt  int 20     2   gt  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

User · Answer

There s little wrong with using array intersect   and count    instead of empty    For example    bFound    count array intersect  criminals   people      true   false

User · Answer

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  lt  10   j                 TEST ONE array intersect               t   microtime true       for  i   0   i  lt  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  lt  100000   i                   x   false          foreach  a2 as  v               if in array  v  a1                                  x   true                  break                                     in array times     microtime true  -  t2     echo   lt hr gt  lt br gt   implode   lt br gt    intersect times    lt br gt array intersect avg     array sum  intersect times    count  intersect times    echo   lt hr gt  lt br gt   implode   lt br gt    in array times    lt br gt 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

User · Answer

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

User · Answer

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

User · Answer

You can use array intersect      result    empty array intersect  people   criminals

User · Answer

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    gt     email          Then  we can set our values that we will check    table    users    column    email    value    alice bob com     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 - gt where  column        value - gt first             if   exists  return response  - gt json    in use    gt  true    200           return response  - gt json    in use    gt  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  - gt json    error    gt   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  - gt json    error    gt   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   and in array   are PHP functions    source    https   php net manual en function array-key-exists php https   php net manual en function in-array php   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    gt     account name    phone    business email          users    gt     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 alice bob com  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

[php] Checking to see if one array's elements are in another array in PHP

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