how to compare 2 arrays using in_array function

Question

i have 2 arrays i need to compare exactly in the same order, i need to check if each array from classes subA and subB contains the value from the one in prerequisite.

my prerequisite array

Array
(
    [s1] => MAT
    [s2] => ENG
    [s3] => PHY
    [s4] => CHE
    [s5] => FRE
)

and my classes array

Array
(
    [subA] => MAT
    [subB] => ENG
)
Array
    (
     [subA] => ENG
     [subB] =>
    )
Array
    (
     [subA] => MAT
     [subB] => PHY
    )
Array
    (
     [subA] => CHE
     [subB] => 
    )
Array
    (
     [subA] => MAT
     [subB] => FRE
    )

my code

$prerequisite = array(
  's1' => 'MAT',
  's2' => 'ENG',
  's3' => 'PHY',
  's4' => 'CHE',
  's5' => 'FRE'
);

$confirmed = TRUE;

$i = 0;
foreach($prerequisite as $p )
{                     
  if( in_array( $prerequisite, $classes[$i] ) )
  {
    // The prerequisite has been met
  }
  else
  {
    // The prerequisite has not been met
    $confirmed = FALSE;
  }
  $i++;
}

if($confirmed == TRUE) { //run insert query here }

expected output

I need to return TRUE if all prerequisites are met, need it to find for example:

if first array from classes subA or subB matches s1 value MAT from prerequisite array
if second array from classes subA or subB matches s2 value ENG from prerequisite array
if third array from classes subA or subB matches s3 value PHY from prerequisite array
if fourth array from classes subA or subB matches s4 value CHE from prerequisite array
if fifth array from classes subA or subB matches s5 value FRE from prerequisite array

Problem

I am always getting FALSE and not being able to run the insert query

@Ikillnukes my classes array is coming from a query running before this condition that's why i posted the output of classes array in my question — mirvatJ, Sep 03 '17 at 20:19

Devon Bessemer · Accepted Answer · 2017-09-03T20:26:14.377

You're not using $p, you're providing an array as the needle argument to in_array(): http://php.net/manual/en/function.in-array.php

If you replace the in_array needle with $p, you'll be searching $classes[$i] for a single value rather than an entire array.

You also don't seem to need that entire block, just use a ! (not) on the condition rather than checking a condition and using an else block.

if( ! in_array( $p, $classes[$i] ) )
{
    $confirmed = false;
}

score 1 · Answer 2 · answered Sep 04 '17 at 11:05

This question provides a beautiful use case for the PHP function array_map():

$prerequisite = array(
  's1' => 'MAT',
  's2' => 'ENG',
  's3' => 'PHY',
  's4' => 'CHE',
  's5' => 'FRE'
);

$classes = array(
    array(
        'subA' => 'MAT',
        'subB' => 'ENG',
    ),
    array(
        'subA' => 'ENG',
        'subB' => NULL,
    ),
    array(
        'subA' => 'MAT',
        'subB' => 'PHY',
    ),
    array(
        'subA' => 'CHEx',        // <---- doesn't match the prerequisite
        'subB' => NULL,
    ),
    array(
        'subA' => 'MAT',
        'subB' => 'FRE',
    ),
);

// array_filter() removes the matching classes
$missing = array_filter(
    array_map(
        function(array $class, $pre, $key) {
            // Return $key when the values of both 'subA' and 'subB'...
            // ... are different than the expected prerequisite
            return ($class['subA'] !== $pre && $class['subB'] !== $pre) ? $key : NULL;
        },
        $classes,
        $prerequisite,
        array_keys($prerequisite)
    )
);


// $missing associates the keys of $classes (numbers) to the keys of $prerequisite
// ... for classes that do not match their prerequisite
print_r($missing);

The output is:

Array
(
    [3] => s4
)

z3nth10n · Answer 3 · 2017-09-03T20:39:31.193

This can be an possible duplicate of: Checking to see if one array's elements are in another array in PHP

You should use array_intersect for this approach...

I will answer because there are also another things that you haven't cleared.

$prerequisite = array(
  's1' => 'MAT',
  's2' => 'ENG',
  's3' => 'PHY',
  's4' => 'CHE',
  's5' => 'FRE'
);

$classes1 = array(
    "subA" => "MAT",
    "subB" => "ENG"
);

$classes2 = array(
    "subA" => "ENG",
    "subB" => ""
);

if(!empty(array_intersect($prerequisite, $classes1))) { 
    //run insert query here
}

You have missed some things:

You have used $classes as a numeric array instead of an associative one.
You have missed $p in the foreach

As you can see, I have created the array from the query that you have told me.

You can see this working on here

how to compare 2 arrays using in_array function

3 Answers3