Assalam o aliekum dosto, aaj may aa sab ko ek bht he simple tariqa btaoun ga or wo bhi full explaination k sath.
Bht say log jb mysql start karty hain tio wo es bat may bht confuse ho jatay hain k unsy php say mysql say connection nahi ban rha to aaj es tutorial may a to btaoun ga k kesay bnaya jata hy. Dosto es tutorial may main ny 110% explain kia hy sari logics k sath k connection kis trah banta hy taaky har bat clear ho jaye.

sb say pehly may ye bta du k mysql bnany wali company ny ab esay upgrade kar k esko MySQLi kar dia hy.. yani end per "i" ata hy ab jiska matlb hy improved or aab aagay yehi chal rahi hay purana sab ditch kar dia geya hy php walo ki taraf say bhi or mysql ki taraf say bhi

Connection:
es k lye php ka ek function use hota hy:
mysqli_connect();
ye function 4 parameters leta hy jo apki database say connection bnaty hain
(i) Internet Service ka Host name
(ii) Username jo apny mysqli may set kia hota hy
(iii) password jo mysqli may set kia hota
(iv) DataBase ka name jis Database say connect karna hy

behtar hy hum en charon ko variable bna k mysqli_connect k function may send kar dein

$hostname = "localhost";
$username = "root";
$password = "";
$dbname = "userRecords";

dosto ye sab default settings hain jo generally use hoti hain mgar professional level pe username or password lazmi different hoty hain or hostname ziadatar localhost he chalta hy....To ab en ko function may send karty hain

mysqli_connect($hostname, $username, $password, $dbname);

php ka ye function humy ek cheese return karta hy jisay kaha jata hy mysqli connection handler or ye handler functions ko ye btata hy k kis db say data use karna hy, ye handler hum 90% say ziada php k functions may use karty hain es lye behtar hy k esko ek variable may store kr lia jaye:

$con = mysqli_connect($hostname, $username, $password, $dbname);

Last step ye hy k hum ye confirm karty hain k connection bana hy k nahi or agr nahi bana to php ko he stop kar dete hain:

if(mysqli_connect_errno()){
die("Connection Failed: ".mysqli_connect_error());
};

to agr connection bnaty huye koi error aya to if k ander jo expression hy yani k mysqli_connect_errno() uski koi na koi value hogi or agar connection ban gya successfully to eski value automatically ho jaye ge false or baqi ki site open ho jye ge. ye function humy db connection ka error num return karta hy.
mysqli_connect_error() ka function humy pura error return karta hy vrna php k apny error msgs apny dekhy he hongy kitny buray lagty hain ye saf suthra error return karta hy..

ye lein dosto full code connection ka...

$hostname = "localhost";
$username = "root";
$password = "";
$dbname = "userRecords";

$con = mysqli_connect($hostname, $username, $password, $dbname);

if(mysqli_connect_errno()){
die("Connection Failed: ".mysqli_connect_error());
};

to li jiye dosto ye full explaination hy k PHP ki script ko aap MySQLi say kesay connect karty hain. umeed hy aap sab ko pasand aye ga. comments zaroor di jiye ga or mera youtube channel zaroor check karein may us per bhi full explain karta hu logics k sath k koi cheese kesay kam karti hy..