php - Checking if username exists in Database jQuery -

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i want check if username taken, here script, outputs "undefined". can me, please? :)

this in jquery - $("#registerusername").val() value of input.

$.post('checkregister.php',{username: $("#registerusername").val()}, function(data){     window.alert(data.exists);     if(data.exists){         window.alert("name found");     }else{         window.alert("name not found");     } }, 'json');

this in checkregister.php

header('content-type: text/json'); if(!isset($_post['username'])) exit; $db = new pdo('mysql:host=localhost;dbname=testdatabase','root','pw000'); $query = $db->prepare("select * users username = '" . $_post['username'] . "'"); $query->execute(); echo json_encode(array('exists' => $query->rowcount() > 0));

first, might want strengthen php against sql injection 'sanitizing' input.

next why return json php? simpler return either true or false.

$db = new pdo('mysql:host=localhost;dbname=testdatabase','root','pw000'); $query = $db->prepare("select * users username = '" . $_post['username'] . "'"); $query->execute(); if( $query->rowcount() > 0 ){     echo 'true'; } else{     echo 'false'; }

then in javascript:

$.post('checkregister.php',{username: $("#registerusername").val()}, function(data){ window.alert(data); if(data == 'true'){     window.alert("name found"); }else{     window.alert("name not found"); } });

edit--- return boolean variable php rather string, either work


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