Converting Javascript function into a PHP function

Question

I am new to PHP and I'm trying to convert a simple Javascript function into a PHP function. So far I know to only convert the variables, I need help with the sort function and array filter. Thanks for any help!

var closeRoll = function( number ) {
  var rollArray = [36, 48, 60, 72];
  var closest = rollArray.filter(function(ele){
    return ele - number >= 0
  }).sort()[0];
  return closest;   
};

My half conversion:

function closeRoll( $number ) { 
  $rollArray = Array(36, 48, 60, 72);
  $closest = array_filter( $rollArray, function temp( $rollArray ) {
    return $rollArray - $number >= 0;
  }); //.sort()[0];
  return $closest;   
};

how did this get upvoted? -1 typing in 'php sort' in google will give thousands of results. — dm03514
– dm03514, Commented Apr 20, 2012 at 16:12
So this function returns all elements in an array that are greater than/equal to the specified number? — Explosion Pills
– Explosion Pills, Commented Apr 20, 2012 at 16:14
@dm03514 I upvoted it. It's a well-stated question (and he made an attempt to solve it on his own). The ease at which you can answer it isn't necessarily relevant. Many questions here are asked primarily because the user doesn't know all of what a language is capable of. He did a great job asking the question, and as such, I would like to encourage him to continue on this path. — Sampson
– Sampson, Commented Apr 20, 2012 at 16:14
I'm trying to sort array based on the parameter $number subtracted by each $rollArray element and not less than zero, then I need the smallest of those subtracted, again, not less than zero. — Joe Fisher
– Joe Fisher, Commented Apr 20, 2012 at 16:18

Kato · Accepted Answer · 2012-04-30 15:15:37Z

3

Scoping does not work quite like JavaScript; you can't simply refer to $number inside your callback function, because it does not have a scope chain.

You either have to make it global (not recommended but simple):

<?php
function doFilter($element) { // this could still be anonymous, but doesn't have to be
   return $element - $GLOBALS['number'] >= 0;
}

function closeRoll( $number ) { 
   $GLOBALS['number'] = $number;
   $rollArray = Array(36, 48, 60, 72);
   $closest = array_filter( $rollArray, 'doFilter' );
   return $closest;   
};
?>

Or you could utilize the use operator (an elegant solution):

<?php

function closeRoll( $number ) { 
   $rollArray = Array(36, 48, 60, 72);
   $closest = array_filter( $rollArray, function( $element ) use ($number) {
     return $element - $number >= 0;
   });
   return $closest;   
};

?>

edited Apr 30, 2012 at 15:15

answered Apr 20, 2012 at 16:28

Kato

40.6k6 gold badges124 silver badges149 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Joe Fisher Over a year ago

This worked for me, I kindly appreciate your help with this. I will study and learn from your code. Thanks.

hakre · Accepted Answer · 2012-04-20 16:21:39Z

3

You're pretty close, the variable scope in PHP is a little different:

function closeRoll( $number ) { 
    $rollArray = Array(36, 48, 60, 72);
    $closest = array_filter( $rollArray, function($rollArray) use ($number) {
        return $rollArray - $number >= 0;
    }); //.sort()[0];
    return $closest;   
}

Basically the different is use ($number) and you don't need to name the temp function.

answered Apr 20, 2012 at 16:21

hakre

200k55 gold badges453 silver badges865 bronze badges

5 Comments

Joe Fisher Over a year ago

I'm currently looking up the use of 'use'... I'm getting 'an unexpected T_FUNCTION' error. Like I said, I'm a noob so I'm trying to get a grasp on variable scope. I think because $number and $rollArray are in a function within another function, some how is not getting passed to the filter function.. I appreciate everyones help!

devdRew Over a year ago

For a big data rows it's not necessary to make an array_filter, cause it goes through all of the array, don't you think that it's better to use some kind of pretty known algorithm? :)

DaveRandom Over a year ago

@JoeFisher if your getting unexpected T_FUNCTION with this code, you're probably on PHP < 5.3. You'll need to use create_function() which is going to make this more interesting... Try

function closeRoll ($number) { $rollArray = Array(36, 48, 60, 72); $closest = array_filter($rollArray, create_function('$rollArray', 'return $rollArray - '.$number.' >= 0;')); return $closest; }

hakre Over a year ago

You need PHP 5.3 or higher for this code, also I have not tested it. Checkout to upgrade your PHP version and let me know if you still run into problems after that.

hakre Over a year ago

@devdRew: That's a bit out of the scope of the question I'd say, but if TS demands something memory optimized I'm willing the chime in.

Giannis Vrentzos · Accepted Answer · 2012-04-20 16:27:40Z

0

Try this

function closeRoll($number) {
    $rollArray = array(36, 48, 60, 72);
    $closest = array_filter($rollArray, function ($rollArray) use ($number) { return $rollArray - $number >= 0; });

    if (!empty($closest))
    {
        sort($closest);
        return array_shift($closest);
    }
    return null;
}

answered Apr 20, 2012 at 16:27

Giannis Vrentzos

1

Comments

Tobias Sjösten · Accepted Answer · 2012-04-20 16:43:19Z

So if I understand the JavaScript correctly, that function returns the closest matching value in rollArray that is greater than the given number parameter?

Here is my solution to it:

function closeRoll($number) {
    $rollArray = array(36, 48, 60, 72);

    $rollArray = array_filter(
        $rollArray,
        function($value) use ($number) {
            return $value - $number >= 0;
        }   
    );  

    return reset(sort($rollArray));
}

You're on the right path when using array_filter(). However when giving it an anonymous function as a callback you're bumping into the first JavaScript vs PHP problem - scoping.

In PHP functions does not automatically share the scope where they are defined. If you need to use something from the currrent scope you need to bring it with you using the use keyword.

Last I use reset() to pull out the first value of the sorted array, which should be the closest matching one. You can't use $rollArray[0] because array_filter() preserves keys and thus 0 might no longer exist.

devdRew · Accepted Answer · 2012-04-22 18:48:35Z

Here is the example to optimize the search, not straight, but using your brains... :)

<?php

function find($number, array $a)
{
    $len = count($a);

    if ($len == 0)
    {
        return null;
    }
    elseif ($len == 1)
    {
        return array_shift($a);
    }

    sort($a, SORT_NUMERIC);

    $first  = array_slice($a, 0, (int) ($len / 2));
    $second = array_slice($a, (int) ($len / 2));

    // No need to check on isset because of if ($len == 0) elseif ($len == 1) 
    if ($second[0] == $number)
    {
        return $number;
    }

    $index = count($first) - 1;    
    if ($first[$index] == $number)
    {
        return $number;
    }

    return abs($number - $first[$index]) <= abs($number - $second[0]) ? find($number, $first) : find($number, $second);
}

$a = array(10, 99, 51, 201, 999, 500, 555, 618);
$n = 75;

echo find($n, $a);

?>

Collectives™ on Stack Overflow

Converting Javascript function into a PHP function

5 Answers 5

1 Comment

5 Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

1 Comment

5 Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related