PHP with input form with text - do a MySQL query when form focus changes -

i looking how make input form handling in php.

what need when user writes data text form (table1), , moves text form (like pressing tab, or selecting mouse), should start , mysql query see if such data written @ table1 existing in matching mysql table.

my goal without pressing submit button. when google checks if username want register exists.

i thinking this:

$duplicate_data_test ="";  if (focus has moved form field - how check ?) {  $query = "select table1 testdatabase table1 = "' . (table1 form below - how data form field without post?) .'";  $result = mysqli_query($con,$query);  if(mysqli_num_rows($result)>0) {     $duplicate_data_test = "this data found in database. choose else";   }  }   echo '<form action="'.htmlspecialchars($_server["php_self"]).'" method="post">';  echo '<input type="text" maxlength="30" name="table1">'; echo '<span class="duplicaterror">'. $duplicate_data_test.' </span>';  echo '<input type="text" maxlength="30" name="table2">';  echo '<input type="submit" value="ok">'; echo '</form>'; 

thank help!

you cannot "interface" check php. "focus has moved form field" has done javascript.

first, build form html

<form name="testform" action="postform.php" method="post" id="myform">     <label>input 1 : </label>     <input type="text" id="in1" value="" name="input1" />     <label>input 2 : </label>     <input type="text" id="in2" value="" name="input2" />     <div style="color:red;font-weight:bold;" id="error"></div>     <button id="submitbutton">submit</button> </form>  

then make checks when user clicks on submit button javascript/jquery & ajax (prevent event form posting) :

$(document).on('click','#submitbutton',function(event){     event.preventdefault();     if($.trim($('#in1').val()) == ''){         //input 1 empty         $("#error").html('input 1 empty');     }//....continue checks 

finally, if checks good, post form

$("#myform").submit(); 

and if checks not display user message!

$("#error").html("message!"); 

i made little example on how (it's not best way it's example) on jsfiddle, check link : http://jsfiddle.net/9ayo89jt/2/

hope helps!