semicolon.

// Example #1 eval() 
$string = 'cup';
$string2= 'coffee';
$str = 'This is a $string with $string2 in it.';
echo $str. "\n"; // outputs: This is a $string with $string2 in it.
eval("\$str = \"$str\";");
echo $str. "\n"; // outputs: This is a cup with coffee in it.

$operation =  "20 - 5"; 
echo $operation; // outputs 20 - 5
echo eval( $operation. ';' );  // it doesn't show anything.
echo eval( 'echo '. $operation. ';' ); // outputs 15
// or
eval( '$temp = ' .$operation. ';' );
echo $temp; // outputs 15

function isSpecialArray($str) {
    $length = strlen($str);
    $count=1;
    for ($i=1; $i<$length; $i++) {
	if ($str[0]="#") {
	    
► // 0123456789abcdefABCDEF
	    if ((ord($str[$i]) > 64 && ord($str[$i]) < 71) || (ord($str[$i]) > 47 && 
	    ord($str[$i]) < 58) || (ord($str[$i]) > 96 && ord($str[$i]) < 103))  {
		$count+=1;
		}
	    }
	}
    if (strlen($str)==7 && $count==$length){
	return true;
    }
    return false;
}
var_dump(isSpecialArray("#CD5C5B"));

true 

false

function validateEmail($email) {
    if ($email == "") {
	return false; "\n";
    }
    $reversed = strrev($email);
    $position = strpos($email, "@");
	if (substr_count($email, "@") == 1 && $position > 0 && ord($email[$position + 1]) > 96 
            && ord($email[$position+1])<123 && substr_count($email, ".") > 0 
            && strpos($reversed, ".") < strpos($reversed, "@") - 1 && $reversed[0] != ".")  {
	        return true; "\n";
	        }
    return false; "\n";
}
echo(validateEmail('@edabit.com')); //false
echo(validateEmail('bill.gates@microsoft.com'));//true

<?php 
function gettingmarried($women, $men) {

$count=count($women); //count-counts the number of women.

// '!=' -If not equal.
if ($women != count($men)) {
echo "I don't have all pairs";
}

//array_combine-Pairs the data of the first element with the second.
return  array_combine($women, $men);
}

print_r(gettingmarried(["elene","mariami"], ["dato", "vano"]));

<?php
function space($sentence) {

$sentence= trim($sentence); //trim function-Breaks a sentence after spaces.

//str_contains-Checks if there is a blank in this sentence in this situation.
while (str_contains($sentence, '  ')) {

// str_replace-Replaces the first element with the second element in this sentence.
$sentence= str_replace('  ', ' ',$sentence);
}
return $sentence;
}
$sentence "  hi     i    am   gvanca";
echo space($sentence);

 <?php
  function isPalindrome($s) {
        //s = "A man, a plan, a canal: Panama"
        $s= strtolower($s);
         $filtered = "";
        $len = strlen($s);
        for ($i= 0; $i<$len; $i++){
            $ascii = ord($s[$i]);
            if (($ascii>=97 && $ascii<123) ||
             ($ascii>47 && $ascii<58)){
                $filtered.=$s[$i];
                }
        }
        return $filtered == strrev($filtered);
    }
   $s = "A man, a plan, a canal: Panama";
   echo isPalindrome($s);

$string = "hello world";
$pattern = "/world/";
echo preg_match($pattern, $string);
// outputs 1

therefore if that case would be like that:

$string = "Hello wORLD";
$pattern = "/world/i";
echo preg_match($pattern, $string);
// it would still outputs 1

For example: (via Regex - Regular Expression and preg_match)
(^[A-Z]*$) it means if there are only uppercase letters in a string.
(^[a-z]+$) it means if there are only lowercase letters in a string.
(^[A-Z]{1}[a-z]*$) it means if the first letter is uppercase in a string.
| - it means "Logical or" via regex as well.

function arrayFillKeys($array) {
    print_r($array);
    $array = array_fill_keys($array, 'value');
    return ($array);
}
print_r(arrayFillKeys([4,3,2]));

function arrayKeys($array) {
    print_r($array);
    return array_keys($array);
}
print_r(arrayKeys(["House" => "White", "Car" => "Black"]));