implode() function is can convert the array to string in PHP.
$array=array("array",,"is""string","now");
echo implode(" ",$array); // it print array is string now
implode("first argument is glue","second argument must be
array ")
so in above we glued the array value with one space and make a string in returns
join() function is can convert the array to string in PHP.
$a=array("a",,"b""c","d");
echo join(" ",$array);
join("first argument is glue","second argument must be array ")
so in above we glued the array value with one space and make a string in returns with join() function in PHP
join() function is alias of the implode() function in PHP
if you want to convert array to JSON string .
json_encode() function will encode array to JSON, JSON is one type of string which formatted so it can convert JSON string to array again.
$response=array("stauts"=>"1");
echo json_encode($response);
JSON format is used to information exchange between server to server or server to client
Server Ajax response will be sent back to the browser in the format of JSON