add number and operators to array PHP

Question

I'm trying to add a row of numbers and operators to an array. How can i do it correctly?

What I wish is to separate each number group to one index and in the next index operator .

I need your help to show me where is the error in my code:

function toArray($s){

    $le = strlen($s);
    $j = 0;
    $ordered_numbers_operators = array();
    $operators = array('+','-','*','/','%','(',')');

    for ( $i=0;$i<$le;$i++ ){

        if ( in_array( $s[$i], $operators )  ) {
            $ordered_numbers_operators[$j] = $s[$i];
            $j++;

        } else {

            if ( $i+1 == $le ){
                $ordered_numbers_operators[$j] = $s[$i];

            } else {

                if ( $s[$i+1] !== in_array( $s[$i+1], $operators ))  {

                    if ( $s[$i+1] == in_array( $s[$i+1], $operators )){
                        echo "\$i = " . $i . "<br />" ;
                        $ordered_numbers_operators[$j]=$s[$i];
                        $j++;

                    } else {

                        $ordered_numbers_operators[$j] = $s[$i] . $s[$i+1];
                        $i++; $j++;
                    }

                }
            }
        }
    }

    return $ordered_numbers_operators;

    }

$string = '6+4*4+100+444*6*13*14';

$arr = toArray($string);

The expected result:

[0] => 6
[1] => +
[2] => 4
[3] => *
[4] => 4
[5] => +
[6] => 100
[7] => +  
[8] => 444  
[9] => *
[10] => 6
[11] => *
[12] => 13
[13] => *
[14] => 14    

The actual result:

[0] => 6
[1] => +
[2] => 4
[3] => *
[4] => 4
[5] => +
[6] => 1
[7] => 0
[8] => 0
[9] => +
[10] => 44
[11] => 4
[12] => *
[13] => 6
[14] => *
[15] => 13
[16] => *
[17] => 14

Answer 1

Without regex, you can do this a lot more simply. See this example, to test and run:

<?php


function toArray($s){
    $operators = array('+','-','*','/','%','(',')');

    $finalArr = [];
    $curStr = '';
    foreach (str_split($s) as $char) {
        if (in_array($char, $operators)) {
            //Alright, we have an operator. Append the entire number
            $finalArr[] = $curStr;
            //And also the operator
            $finalArr[] = $char;
            //Reset the current string back to empty
            $curStr = '';
        } else {
            //Not an operator? Just keep appending the current number
            $curStr .= $char;
        }
    }

    //Add final leftover string
    if ($curStr !== '') { //Sanity check here (This shouldn't ever be empty, as you wouldn't end with an operator)
        $finalArr[] = $curStr;
    }

    //Return
    return $finalArr;
}

$string = '6+4*4+100+444*6*13*14';

$arr = toArray($string);

print_r($arr);

Answer 2

You can do it with a regex and preg_split, a bit easier.

$parts = preg_split('~([+*/-])~', '6+4*4+100+444*6*13*14', -1, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY);
print_r($parts);

Demo: https://3v4l.org/oCrLG

Note the - as the last character in the character class is important. If you add more characters after that the - will create a range between the closest character on each side. Any characters you want to separate on can be added inside the []. If adding ] though be sure to escape it so the closure is correct. You can read more about character classes here, https://www.regular-expressions.info/charclass.html.

The character class also makes it so you don't need to escape special regex characters. You could also do it like this, which removes the character class.

$parts = preg_split('~(\+|\*|/|-)~', '6+4*4+100+444*6*13*14', -1, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY);
print_r($parts);

Demo: https://3v4l.org/Jha6P

Additionally whitespace can be made optional with \s* or \h* before and after the operators.

$parts = preg_split('~\h*([+*/-])\h*~', '6+4*4+100+444*6*13*14', -1, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY);
print_r($parts);

Answer 3

Another regex-free way is to use array_reduce.

You can use str_split to split the string into an array, and then use array_reduce to build your desired array (so that consecutive numbers are joined). Let's do that step by step. First, with a simple callback function in array_reduce, we get the same result as with str_split:

function toArray($string) {
    $chars = str_split($string);

    return array_reduce($chars, function($result, $current) {
        $result[] = $current;

        return $result;
    }, []);
}

$input = '6+4*4+100+444*6*13*14';
print_r(toArray($input));

/*
Array
(
    [0] => 6
    [1] => +
    [2] => 4
    [3] => *
    [4] => 4
    [5] => +
    [6] => 1
    [7] => 0
    [8] => 0
    [9] => +
    [10] => 4
    [11] => 4
    [12] => 4
    [13] => *
    [14] => 6
    [15] => *
    [16] => 1
    [17] => 3
    [18] => *
    [19] => 1
    [20] => 4
)
*/

Next step is to check the previous value and the current value when iterating over the characters in array_reduce. If they are both numbers, we want to join them:

function toArray($string) {
    $chars = str_split($string);

    return array_reduce($chars, function($result, $current) {
        $previous = $result[] = array_pop($result);

        if (is_numeric($previous) && is_numeric($current)) {
            $result[] = array_pop($result) . $current;
        } else {
            $result[] = $current;
        }

        return $result;
    }, []);
}

$input = '6+4*4+100+444*6*13*14';
print_r(toArray($input));

/*
Array
(
    [0] =>
    [1] => 6
    [2] => +
    [3] => 4
    [4] => *
    [5] => 4
    [6] => +
    [7] => 100
    [8] => +
    [9] => 444
    [10] => *
    [11] => 6
    [12] => *
    [13] => 13
    [14] => *
    [15] => 14
)
*/

Almost there! The array contains one extra element at index zero. (That's because we are getting the previous item with $previous = $result[] = array_pop($result);. Its value is null, because initially $result is an empty array, so array_pop returns null.) We can get rid of the extra element e.g. with array_slice:

function toArray($string) {
    $chars = str_split($string);

    $array = array_reduce($chars, function($result, $current) {
        $previous = $result[] = array_pop($result);

        if (is_numeric($previous) && is_numeric($current)) {
            $result[] = array_pop($result) . $current;
        } else {
            $result[] = $current;
        }

        return $result;
    }, []);

    return array_slice($array, 1);
}

$input = '6+4*4+100+444*6*13*14';
print_r(toArray($input));

/*
Array
(
    [0] => 6
    [1] => +
    [2] => 4
    [3] => *
    [4] => 4
    [5] => +
    [6] => 100
    [7] => +
    [8] => 444
    [9] => *
    [10] => 6
    [11] => *
    [12] => 13
    [13] => *
    [14] => 14
)
*/

Demo: https://3v4l.org/qZsvs