function that gets the item that occurred an odd number of times in an array.

getOddOccurenceFromArray.php

<?php

// first solution
function getOddOccurrenceFromArray1($arr) 
{ 
    $result = 0;  
    for ($i = 0; $i < sizeof($arr); $i++)      
    /*
     * Using xor bitwise operator, the final value of $result will
     * be the array item that occurred an odd number of time
     */
    $result = $result ^ $arr[$i]; 
      
    return $result; 
}

//second solution
function getOddOccurrenceFromArray2($arr) {
    
    $countedArray = array_count_values($arr);

    $filteredArray = array_filter($countedArray, function ($value, $key) {
        return $value % 2 != 0 ;
    }, ARRAY_FILTER_USE_BOTH);

    $arrayKeys = array_keys($filteredArray);

    return $arrayKeys[0];

}

/*
* input array: [1,1,1,3,4]
*/

/*
* output: 1
*/