function containsDuplicate($nums) {
    $nums = array_count_values($nums);
    foreach ($nums as $key => $num) {
	if ($num >= 2) {
	    return true;
	}
    }
    return false;
}
echo containsDuplicate([1, 2, 3, 1]);

function thirdMax($nums) {
    $nums = array_unique($nums);  // built-in function that removes duplicated values in array
    sort($nums);
    $count = count($nums);
    if ($count >= 3) {
	array_pop($nums);
	array_pop($nums);
    }
    return end($nums); // built-in function that returns the last element of array
}
echo thirdMax([2, 2, 3, 1]);

function isValid($string) {
    $len = strlen($string);
    $filtered = '';
    for ($x = 0;  $x < $len;  $x++) {
	$ASCII = ord($string[$x]);
	if (($ASCII==91 || $ASCII==93 || $ASCII==123 || $ASCII==125 || $ASCII==40 || $ASCII==41)) {
		$filtered .= $string[$x];
	}
    }
    $len2 = strlen($filtered);
    if($len2%2==1){
    return false;
    }
    $parentheses = [
	"("=>")", 
	"["=>"]" , 
	"{"=>"}",
    ];
    $open = [];
    for ($x = 0;  $x < $len2;  $x++) {
	if (array_key_exists($filtered[$x], $parentheses)) {
		array_push($open, $filtered[$x]);
	} else {
		$parenthesis = array_pop($open);
		if ($filtered[$x] != $parentheses[$parenthesis]) {
			return false;
		}
	}
    }
    if ($open) {
	return false;
    }
    return true;
}
echo isValid("{ :'> baeknwaw adanww a} [ daw  ] awda( :.a,a)a"); // returns true
echo isValid("(1 + 1) = 2"); // returns true
echo isValid("(1 + 1)) = 2"); // returns false
// enjoy with coding))

function missingNumber($nums) {
    sort($nums);
    foreach ($nums as $key => $num) {
        if ($key != $num) {
            return $key;
        }
    }
    return count($nums);
}

function intersection($nums1, $nums2) {
    // firstly, remove duplicates, 
    // you can use here array_unique function twice !
    $result1 = [];
    $result2 = [];
    foreach ($nums1 as $num1) {
    	if (!in_array($num1, $result1)) {
    		$result1[] = $num1;
        }
    }
    foreach ($nums2 as $num2) {
    	if (!in_array($num2, $result2)) {
    		$result2[] = $num2;
        }    
    }
    // merge two arrays
    // you can use here array_merge function !
    for ($i = 0;  $i < count($result2);  $i++) {
        $result1[$i + count($result1)] = $result2[$i];
    }
    $array = [];
    // unfortunately, I could not count the values ​​and 
    // get the keys from array without built-in function
    $result1 = array_count_values($result1);
    foreach ($result1 as $key => $value) {
    	if ($value >= 2) {
    		$array[] = $key;
    	}
    }
    return $array;
}
print_r(intersection([4, 9, 5], [9, 4, 9, 8, 4]));   // [4, 9];

/**
 * @param Integer[] $nums
 * @param Integer $target
 * @return Integer[]
 */
function twoSum($nums, $target) {
	// calculate length of array - $nums
    $nums_len = count($nums);
    // iterate over $nums array
    for($i = 0; $i < $nums_len; $i++){
    	// find difference between $target and current number
        $diff = $target - $nums[$i];
        // remove that number and search index of current 
        // number in the $nums array
        unset($nums[$i]);
        $j = array_search($diff,$nums);
        // if there is an element return answer
        if($j != NULL){
            return [$i, $j];
        }
    }
}

/**
 * @param String $s
 * @param String $t
 * @return String
 */
function findTheDifference($s, $t) {
    $len_s = strlen($s);
    $sum_s = 0;
    $sum_t = 0;
    $i = 0;
    // calculate sum of strings by ascii codes numbers
    for(; $i < $len_s; $i++){
        $sum_s += ord($s[$i]);
        $sum_t += ord($t[$i]);
    }
    // so $len_s + 1 == $t 
    // length thats why
    $sum_t += ord($t[$i]);
    return chr($sum_t - $sum_s);
}

/**
* @param Integer[] $nums
* @return NULL
*/
function moveZeroes(&$nums) {
        $nums_len = count($nums);
        for($i = 0; $i < $nums_len; $i++){
            if($nums[$i] === 0){
                unset($nums[$i]);
                $nums [] = 0;
            }
        }
}   

<?php
$a = 0;
// True because $a is set
if (isset($a)) {
  echo "Variable 'a' is set.<br>";
}

$b = null;
// False because $b is NULL
if (isset($b)) {
  echo "Variable 'b' is set.";
}
?>

$firstName=["gela", "bela", "lela"];
$age = [18, 19, 20];
$keyValue = array_combine($firstName, $age);
print_r($keyValue);
// ( "gela" => 18,  "bela" => 19, "lela" => 20 )