Question 418911 in PHP Question posted in
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Getting elements after each key element occurence PHP Array

I have an array with following elements:

$array = ["START","a","a","a","START","b","b","b","START","c","c","c"];

I need to get only the elements of the array AFTER every occurence of the key element "START" into their own array:

Example:

$arr[0] = ["a","a","a"];
$arr[1] = ["b","b","b"];
$arr[2] = ["c","c","c"];

I can then break down each individual array and process how I need.

Thanks!

I’ve played with array slice and such, which seemed to be the closest answer but to no avail.

Tags:

3

Answers


  1. 0

    Design: Collect each element using START as a delimiter.

    Implementation:

    $array = ["START", "a", "a", "a", "START", "b", "b", "b", "START", "c", "c", "c"];
$result = [];
$tempArray = [];

// Loop through each element in the original array
foreach ($array as $element) {
    if ($element === "START") {
        // If we encounter "START" and $tempArray is not empty, add it to $result
        if (!empty($tempArray)) {
            $result[] = $tempArray;
            $tempArray = []; // Reset for the next segment
        }
    } else { // The element was not START, so we add this to the tempArray
        // Collect elements in the temp array
        $tempArray[] = $element;
    }
}

// Don't forget to add the last collected array if it exists
if (!empty($tempArray)) {
    $result[] = $tempArray;
}

// Output the result for verification
print_r($result);

    Note that in PHP, the [] syntax is a shorthand way to append an item without needing to specify an index.

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  2. 0

    An approach to this would be to loop through each element and spliting on each encounter of ‘Start’

    $array = ['START', 'a', 'a', 'a', 'START', 'b', 'b', 'b', 'START', 'c', 'c', 'c'];

$new_array = []; // new array to write to 
$counter = 0; // default counter for 'start' occurence
foreach ($array as $arr) {
    //checking occurance / encounter for 'START'
    if ($arr === 'START') {
        $counter++;
    }
    else {
        if(!$new_array) 
        {
            $counter = 0;
        }
        $new_array[$counter][] = $arr; //add to array
    }

}
print_r($new_array);

    which would give you a result of

    (

[0] => Array
    (
        [0] => a
        [1] => a
        [2] => a
    )

[1] => Array
    (
        [0] => b
        [1] => b
        [2] => b
    )

[2] => Array
    (
        [0] => c
        [1] => c
        [2] => c
    )
)
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  3. 0

    Simple and Performing Solution – O(n)

    $array = ["START","a","a","a","START","b","b","b","START","c","c","c"];
$res = [];
$index = 0;
foreach ($array as $val) {
    if ($val === 'START') {
        $index++;
    } else if ($index > 0) {
        $res[$index - 1][] = $val;
    }
}
var_dump($res);
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