Question

By example:

FirstString='apple,gold,nature,grass,class'
SecondString='gold,class'

---

the Result must be :

ResultString='apple,nature,grass'

Answer 1

this is the easy way (for sure there must be more efficient ones):

First of all, you may want to separate those coma-separated strings and put them into an array (using the explode function):

$array1 = explode(',' $firstString);
$array2 = explode(',' $secondString);

Then, you can loop the first array and check whether it contents words of the second one using the in_array function (if so, delete it using the unset function):

// loop
foreach( $arra1 as $index => $value){
    if( in_array ( $value , $array2 ) )
        unset($array1[$index]); // delete that word from the array
}

Finally, you can create a new string with the result using the implode function:

$result = implode(',' , $array1);

That’s it 😀