array_intersect() with 2d arrays in php

Question

I am trying to filter 2d arrays which satisfy two conditions. But, it not works as expected. I figured out that error is in array_intersect() function. Why array_intersect() not works correctly here.Is there another way to do this without iteration.

<?php
            error_reporting(0);
            $students = [
                ["name"=> 'k. l.james', "grade"=>8],
                ["name"=> 'k. l.james', "grade"=>9],
                ["name"=> 'e. musk', "grade"=>8],
                ["name"=> 'jone', "grade"=>9],
            ];
        
            function filterByGrade($grade){
                global $students ;
                if (empty($grade)){
                    return $students ;
                }else{
        
                return array_filter($students , function($record) use($grade){
                    return ($record['grade'] == $grade);
                });
            }
            }
        
            function filterByName($name){
                global $students;
                if (empty($name)){
                    return $students;
                }else{
                
                return array_filter($students, function($record) use($name){
                    return (strcasecmp(str_replace(' ','',$record['name']),str_replace(' ','',$name)) == 0);
                });
            }
            }
            print_r(filterByGrade(8));
            echo "<br/>";
            print_r(filterByName('k.l.james'));
            echo '<br/>';
            print_r(array_intersect(filterByGrade(8), filterByName('k.l.james')));
        ?>

results are;

    Array ( [0] => Array ( [name] => k. l.james [grade] => 8 ) [2] => Array ( [name] => e. musk [grade] => 8 ) )
    Array ( [0] => Array ( [name] => k. l.james [grade] => 8 ) [1] => Array ( [name] => k. l.james [grade] => 9 ) )
    Array ( [0] => Array ( [name] => k. l.james [grade] => 8 ) [2] => Array ( [name] => e. musk [grade] => 8 ) )

I expect the last line of result as,

    Array ( [0] => Array ( [name] => k. l.james [grade] => 8 ))

If I interchanged the two arrays in array_intersect() as follows, the results are different.

    print_r(array_intersect(filterByName('k.l.james'),filterByGrade(8)));

Then,I get result as follows.

    Array ( [0] => Array ( [name] => k. l.james [grade] => 8 ) [2] => Array ( [name] => e. musk [grade] => 8 ) )
    Array ( [0] => Array ( [name] => k. l.james [grade] => 8 ) [1] => Array ( [name] => k. l.james [grade] => 9 ) )
    Array ( [0] => Array ( [name] => k. l.james [grade] => 8 ) [1] => Array ( [name] => k. l.james [grade] => 9 ) )

I noticed that only the first filtered array in array_intersect() is printed despite of considering the intersection of the two arrays.

Note : The string _"k.l.james"_ is defined _"k. l.james"_ in initial array. — Syscall, Feb 27 '21 at 06:33

Syscall · Accepted Answer · 2021-02-28T15:52:33.800

You can create a function to filter students using multiple conditions, instead of trying to combine the 2 results.

The function :

/**
 * Here, $condition array of keys/values used to filter $data.
 * ex: ['name' => 'jone', 'grade' => 9]
 */
function filterArray($data, $conditions)
{
    if (empty($conditions)) {
        return $data;
    }
    
    return array_filter($data, function($record) use ($conditions) {
        // Check all given conditions
        foreach ($conditions as $key => $value) {
            // If doesn't match, return false (don't keep in filtered array)
            if ($record[$key] != $value) return false;
        }
        // conditions passed, add to array
        return true;
    });
}

Usage :

$students = [
    ["name"=> 'k. l.james', "grade" => 8],
    ["name"=> 'k. l.james', "grade" => 9],
    ["name"=> 'e. musk', "grade" => 8],
    ["name"=> 'jone', "grade" => 9],
];

print_r(filterArray($students, ['grade' => 8]));
// out : [["name"=> 'k. l.james', "grade" => 8],["name"=> 'e. musk', "grade" => 8]]

print_r(filterArray($students, ['name' => 'k. l.james']));
// out : [["name"=> 'k. l.james', "grade" => 8], ["name"=> 'k. l.james', "grade" => 9]]

print_r(filterStudents($students, ['grade' => 8, 'name' => 'k. l.james']));
// out : [["name"=> 'k. l.james', "grade" => 8]]

Additional notes :

using global is discouraged, in the code below, $students are given by the function parameter.
No need to use the else statement after a "return early" pattern (if ($someCondition) { return; } else { }).

score 1 · Answer 2 · edited Feb 27 '21 at 13:40

1

array_intersect() functions correctly, if inner array objects are serialized. So, I got correct results by

print_r(
    array_map('unserialize',
        array_intersect(
            array_map('serialize', filterByName('k.l.james')),
            array_map('serialize', filterByGrade(8))
        )
    )
);

Can I know what is more efficient for a website filter , @Syscall's answer or my method.

edited Feb 27 '21 at 13:40

Syscall

19,327
10
37
52

answered Feb 27 '21 at 10:05

Ishad

121
1
11

Interesting answer, but a little bit complicated IMO (array_map / serializing / unserializing), and pretty difficult to read :) My answer allows to do only one loop on the students array (using array_filter). Anyway, the efficiency is probably dependent of the amount of data, and usage. – Syscall Feb 27 '21 at 13:38

score 0 · Answer 3 · answered Mar 25 '23 at 07:27

A concise solution is to make calls of array_intersect_assoc() inside of an array_filter() call -- assuming you have a flat, associative array of qualifying elements.

$students = [
    ["name" => 'k. l.james', "grade" => 8],
    ["name" => 'k. l.james', "grade" => 9],
    ["name" => 'e. musk', "grade" => 8],
    ["name" => 'jone', "grade" => 9],
];

$filterBy = ["name" => 'k. l.james', "grade" => 8];

var_export(
    array_filter(
        $students,
        fn($row) => !array_intersect_assoc($filterBy, $row)
    )
);

Effectively, a given row has the necessary associative data to empty the filterBy array, then the row should be retained.

array_intersect() with 2d arrays in php

3 Answers3