Trying to check if username already exists in MySQL database using PHP

Question

I ve looked at the many other posts that were similar to my issue and implemented their solutions  as far as I can tell  as exactly as I could  However  every time I execute this script  the code in the else block is executed  even when the username inputted is one that is already present    The table name is  Users  and the column that I am trying to search is  username   The input from my form was read into  username and I verified that it was read in properly using echo   con contains the connection to the server   At some point I also put in echo  query  nothing was printed  and echo mysql num rows  query   nothing was printed    Here s the relevant segment of the code  Would really appreciate some tips    query   mysql query  SELECT username FROM Users WHERE username  username    con      if  mysql num rows  query     0            echo  Username already exists          else                   EDIT  Apparently I was supposed to be using mysqli for my server and the way I checked the num rows for that was by doing  query- num rows since it was a property of the object  Thanks for all the help

User · Answer

Everything is fine  just one mistake is there  Change this    query   mysql query  SELECT username FROM Users WHERE username  username    con    query   mysql query  SELECT Count    FROM Users WHERE username  username   con     if  mysql num rows  query     0        echo  Username already exists     else             SELECT   will not work  use with SELECT COUNT

User · Answer

TRY THIS ONE   mysql connect  localhost   dbuser   dbpass      query    SELECT username FROM Users WHERE username     username      mysql select db  dbname          result mysql query  query       if  mysql num rows  query     0            echo  Username already exists              else

User · Answer

firstname     POST  firstname     lastname     POST  lastname     email     POST  email     pass     POST  password      check email   mysqli query  conn   SELECT Email FROM crud where Email     email      if mysqli num rows  check email   gt  0       echo  Email Already exists      else      if    SERVER  REQUEST METHOD       POST          result   mysqli query  conn   INSERT INTO crud  Firstname  Lastname  Email  Password  VALUES    firstname     lastname     email     pass            echo  Record Entered Successfully

User · Answer

query   mysql query  SELECT username FROM Users WHERE username   username      Use prepared statements  do not use mysql as it is deprecated      check if name is taken already  stmt    link- gt prepare  SELECT username FROM users WHERE username    username     stmt- gt execute        username    gt   username      user    stmt- gt fetch PDO  FETCH ASSOC    if  isset  user   amp  amp   empty  user           Username already taken

User · Answer

Here s one that i wrote     error   false   sql   SELECT username FROM users WHERE username     username     checkSQL   mysqli query  db   checkSQL    if mysqli num rows  checkSQL     0        error   true     echo   lt span class  error  gt Username taken  lt  span gt        Works like a charm

User · Answer

PHP 7 improved query             sql   mysqli query  conn   SELECT   from users WHERE user uid     uid           if  mysqli num rows  sql   gt  0             echo  Username taken

User · Answer

Try this    query   mysql query  SELECT username FROM Users WHERE username   username       Don t add  con to mysql query   function   Disclaimer  using the username variable in the string passed to mysql query  as shown above  is a trivial SQL injection attack vector in so far the username depends on parameters of the Web request  query string  headers  request body  etc   or otherwise parameters a malicious entity may control

User · Answer

change your query to like    username   mysql real escape string  username      escape string before passing it to query   query   mysql query  SELECT username FROM Users WHERE username     username           However  MySQL is deprecated  You should instead use MySQLi or PDO

[php] Trying to check if username already exists in MySQL database using PHP

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