Filter array with variable and keep results

Question

I have and array:

Array(
  [9533]=>44
  [6478]=>56
)

I want to filter the array with a variable. I have tried this:

function filterArray($value){
    return ($value == $myVar);
}

$filteredArray = array_filter($myArray, 'filterArray');
print_r($filteredArray);

it just prints:

array()

if I change the variable to a hard number like 44, then it will give me what I want.

Array(
  [9533]=>44
)

the filterArray doesn't know what $myVar you are looking to match. — Biotox
– Biotox, Commented Aug 13, 2012 at 21:33
This is where closures with a "use" are particularly useful: $myVar = 44; $filteredArray = array_filter($myArray, function($value) use ($myVar) { return $value == $myVar; } ); — Mark Baker
– Mark Baker, Commented Aug 13, 2012 at 21:34
You probably want to declare global $myVar; in the beginning of filterArray() — Nir Alfasi
– Nir Alfasi, Commented Aug 13, 2012 at 21:34

Community · Accepted Answer · 2017-05-23 10:34:39Z

3

Don't use globals, that's a bad idea

$myVar = 44; 
$filteredArray = array_filter( $myArray, 
                               function($value) use ($myVar) {
                                   return $value == $myVar;
                               }
                             );

edited May 23, 2017 at 10:34

CommunityBot

11 silver badge

answered Aug 13, 2012 at 21:47

Mark Baker

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Comments

Alex Kalicki · Accepted Answer · 2012-08-13 21:43:25Z

0

If $myVar is defined outside of the filterArray callback function, you need to declare it global within the function before you can use it. So if you change your filterArray callback to this, then it should work:

function filterArray($value){
    global $myVar;
    return ($value == $myVar);
}

DEMO

Try to avoid using the global keyword when you don't need to. For most functions you can pass the variable as an argument instead. In your case, the global is necessary since array_filter does not allow callbacks with parameters.

answered Aug 13, 2012 at 21:43

Alex Kalicki

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6 Comments

j0k Over a year ago

I said, no please, don't incite him to use global...

Alex Kalicki Over a year ago

Would you like to explain why it's such a bad idea instead of just downvoting? Obviously they're considered bad practice but this really isn't a situation where it will hurt.

j0k Over a year ago

If he starts to learn PHP, it will be preferable that he doesn't try to use global every time he wants to retrieve a variable that isn't in the scope of the function. It will become hard and hard to maintain and understand his code. I never used global and every code I read don't use global.

Tyler Nichol Over a year ago

Thanks for all the quick responses. I cannot declare the variable right before the function because the variable is a user input. Global works great! Please explain why I shouldnt use it.

j0k Over a year ago

A more detailled answer why global is evil

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