Checking if all values in one array exist in another array

Question

I am trying to check if all required values exist in an array. I thought using array_intersect would be what I should be using:

$required[0] = 'FirstName';
$required[1] = 'LastName';

$posted['Email'] = '[email protected]';
$posted['FirstName'] = 'Bob';
$posted['Group'] = '5';

print_r(array_intersect($required, $posted));

So, I want to be sure that "FirstName" and "LastName" exist in the $posted array. However, "LastName" is missing, but this returns an empty array result.

What am I missing?

Don't Panic · Accepted Answer · 2016-08-27 01:07:25Z

1

If $posted originally comes from $_POST at some point, (as in the values from inputs on a form), all of the keys will be set, even though some may be set to ''. Since you have keys as values in your $required array, It's probably best to just check the required fields in a loop. You can use empty to simultaneously verify that they exist and have truthy values. Assuming the following code is the body of a function or the contents of a file, something like this should work:

foreach ($required as $requirement) {
    // if everything has to have a value, just return false as soon as something doesn't
    if (empty($posted[$requirement]) return false;
}
return true;

Part of why the way you're doing it with array_intersect isn't working because that function will check the values in $required against the values in $posted, and you need to check the values in $required against the keys in $posted. The other part is that array_intersect will return the values that the two arrays have in common, not the ones that are missing.

If some of the keys in $posted really may not exist, it may be better to define your $required array by key instead of by value, and then use array_diff_key.

$required['FirstName'] = true;
$required['LastName'] = true;

$missing_requirements = array_diff_key($required, $posted);

If every key in $required is present in $posted, the result will be an empty array, which will evaluate to false.

edited Aug 27, 2016 at 1:07

answered Aug 27, 2016 at 0:46

Don't Panic

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2 Comments

MultiDev Over a year ago

Thank you for your answer. I'm surprised that I'm finding that just checking if (empty())... for all the required fields is about 50% faster on average. I thought this would be much faster.

Don't Panic Over a year ago

Well, it has the advantage of no function calls, and if you do it like I suggested, you don't actually have to look through everything, you can stop looking as soon as you find one missing thing.

Andrej · Accepted Answer · 2016-08-27 00:42:28Z

0

print_r(array_intersect($required, array_keys($posted)));

Simple solution:

if (count(array_intersect($required, array_keys($posted))) == count($required) ) { 
return true;
} else {
return false;
}

edited Aug 27, 2016 at 0:42

answered Aug 27, 2016 at 0:38

Andrej

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3 Comments

MultiDev Over a year ago

This returns all of the values in $required that exist in $posted. I basically just need to return true if all exist or false if not.

Andrej Over a year ago

If (count(array_intersect($required, array_keys($posted))) == count($required) ) { return true;} else {return false;} @JROB

Solomon Closson Over a year ago

count is no good if you are matching array values that could have different results and the array count gets changed dynamically.

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