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how to pass php variable to javascript?

I am using following code to pass PHP variables to javascript. but it is not working.
function gto(str) {
document.getElementById('goto').action = str;
document.getElementById('ID').value = <?php echo "$userid" ?>;
document.getElementById('name').value = <?php echo "$user_name" ?>;
document.getElementById('gname').value = <?php echo "$usergname" ?>;
document.getElementById('fmname').value = <?php echo "$userfname" ?>;
document.getElementById('img').value = <?php echo "$userimg" ?>;
document.getElementById('email').value = <?php echo "$useremail" ?>;
document.getElementById('goto').submit();
}
Following is the PHP code
<?php
if($_POST["name"] == null)
{
$user_name = 'Annomyous';
}
else{
$user_name = $_POST["name"];
$userid= $_POST["id"];
$usergname= $_POST["gname"];
$userfname= $_POST["fname"];
$userimg= $_POST["img"];
$useremail= $_POST["email"];
}
echo "<p style='color : white'>$user_name";
echo "$userid" ;
echo "$gname";
echo "$fname";
echo "$img";
echo "$email";
echo "$user_name";
echo "$user_name</p>";
$user_name =htmlspecialchars($user_name);
$user_name =str_replace("<script>","", $user_name);
?>
the output is a follows:
ReAlItY TuTs104598758504708047866ReAlItY TuTsReAlItY TuTs//this is php echo output.
JAVASCRIPT OUTPUT:-
function gto(str) {
document .getElementById('goto').action = str;
document.getElementById('ID').value = ;
document.getElementById('name').value = Annomyous;
document.getElementById('gname').value = ;
document.getElementById('fmname').value = ;
document.getElementById('img').value = ;
document.getElementById('email').value = ;
document.getElementById('goto').submit();
}
Function gto is called here:
<button class="w3-btn header-btn" onclick="gto('Contact.php');">Contact Us</button>
I can see in PHP output I am getting all variable output.
but nin juavascript im getting only Annonymous why????
I need to pass post variables to contact us so i am using the form tag and javascript but this is not working Please help me!
Thanks in Advance

values from php to js can be passed in many ways, here's one of them
try to pass the php values when calling the js function, like this:-
<button onclick="gto('Contact.php','<?php echo $userid;?>','<?php echo $username;?>');">Contact Us</button>
and then get values on js function like this:-
function gto(str,userid,username) {
document .getElementById('goto').action = str;
document.getElementById('ID').value = userid;
document.getElementById('name').value =username;
}
that's it, now use the values in js as your wish

Uh, found another issue. The js is in smart quotes, which won't work... "`" is invalid. use "'".
Also, w3schools can't handle php in their editor, so it's no use.
Example for POST requests: https://www.w3schools.com/code/tryit.asp?filename=FQSA8MJYGJ47
Hope this helps.

Get javascript variable value in php

I need to get javascript variable value in php file.
html example:
UPDATE:
$html = '
<script>
window.runParams.adminSeq="3423423423423";
window.runParams.companyId="2349093284234";
</script>';
Shout I use regex ? regex is very complex to me... any help ?

<?php
$html = '<script>
window.runParams.adminSeq="3423423423423";
window.runParams.companyId="2349093284234";
</script>';
$variables = ["adminSeq", "companyId"];
$counter = 0;
foreach($variables as $variable) {
preg_match_all('/"(.*?)"/', $html, $matches);
${"$variable"} = ($matches[1])[$counter];
$counter++;
}
echo $adminSeq; // Prints out: 3423423423423
echo $companyId; // Prints out: 2349093284234
?>
You can also use GET requests to do this. The link would look like http://localhost/?adminSeq=3423423423423&companyId=2349093284234 then get out these values in PHP with:
<?php
$adminSeq = $_GET["adminSeq"];
$companyId = $_GET["companyId"];
?>

Only getting the last row in materialize select

How do I change the value of a SELECT tag in MATERIALIZE CSS. I'm trying show the selected item that was stored from the database. I tried adding .material_select() at the end of the select but it only retrieves the LAST one in the row. How do I show every try ? Here's what I've tried so far.
$(function() {
<?php
$q = $db->query("SELECT buildingID, buildingName,building_projectID, floorNumber FROM tblBuilding");
while($r = $q->fetch(PDO::FETCH_ASSOC)){
$buildingID = $r['buildingID'];
$buildingName = $r['buildingName'];
$building_projectID = $r['building_projectID'];
$floorNumber = $r['floorNumber'];
$t = $db->query("select projectName from tblProject where projectID = $building_projectID ");
while($u = $t->fetch(PDO::FETCH_ASSOC)){
$projectName = $u['projectName'];
?>
$("#editModal<?php echo $buildingID ?>").click(function(){
alert('<?php echo $projectName ?>');
$("#editBuildingName").val("<?php echo $r['buildingName'] ?>");
$("#editBuildingProject").val("<?php echo $projectName");
$("#editBuildingFloors").val("<?php echo $floorNumber ?>");
});
<?php }}?>
});

instead of:
$("#editBuildingProject").val("<?php echo $projectName");
use this:
$("#editBuildingProject").val("<?php echo $building_projectID ?>").material_select('update');

How to use php with sql query in javascript

var phpCode = '<?php
$sql = "SELECT Name,Surname,id_room FROM timatable.professors WHERE p.id_professor = '".mysqli_real_escape_string($_POST['hiddenProfId'])."'";
$resutl = mysqli_query($db,$sql);
if ($result == 1 ) {
$row = mysqli_fetch_array($result);
$professorName = $row['Name'];
$professorSurname = $row['Surname'];
} else echo "Error";
?>';
alert(phpCode);
this is my code. how to make it work ????

Try this.
First initialize, variables to null.
$professorName = "";
$professorSurname = "";
This is because, if php code enters else part, you will not get any error in javascript part.
<?php
$sql = "SELECT Name,Surname,id_room FROM timatable.professors WHERE p.id_professor = '".mysqli_real_escape_string($_POST['hiddenProfId'])."'";
$resutl = mysqli_query($db,$sql);
if ($result == 1 ) {
$row = mysqli_fetch_array($result);
$professorName = $row['Name'];
$professorSurname = $row['Surname'];
} else echo "Error";
?>
<script>
var professorName = "<?php echo $professorName ?>";
var professorSurname = "<?php echo $professorSurname ?>";
alert(professorName);
alert(professorSurname);
</script>

PHP is a server-side language. So it is processed on a server. Therefore you cannot have a PHP code in javascript.
If you want to have javascript managed some editing in database, you can use AJAX to do it without reloading the page.

Assigning PHP Variables To Javascript Variables Not Working

I am currently having trouble with this. I would like to make one of my variables in Javascript have a PHP value. Here is what I mean:
<script>
JSvariable = <?php echo $PHPvariable; ?>;
</script>
For some reason that is not working. Here is my full (snippet) of code:
<script>
currentreplyid = <?php echo $allpostcomments[$key]['replyid']; ?>;
$('#parentcommentholder').val(currentreplyid);
</script>
I am sure it is some stupid mistake, but I can not seem to find it! What is the problem? Thank you!
PS #parentcommentholder is an input field, and it just had the value 0 after the field is supposed to of been changed.
Here is some source:
<?php
$postcommentsquery = "SELECT * FROM comments WHERE parent = :parent AND postid = :postid ORDER BY datecreated DESC";
$postcommentsparams = array(':parent' => $allreplies[$key]["postid"],
':postid' => $postid);
try{
$postcommentsstmt = $connection->prepare($postcommentsquery);
$postcommentsresult = $postcommentsstmt->execute($postcommentsparams);
}
catch(PDOException $ex){
echo ("Failed to run query: " . $ex->getMessage());
}
$allpostcomments = $postcommentsstmt->fetchAll();
foreach ($allpostcomments as $key => $value) {
?>
<script>
var currentreplyid = <?php echo $allpostcomments[$key]['replyid']; ?>;
$('#parentcommentholder').val(currentreplyid);
</script>
<input id="parentcommentholder"></div>

Don't forgot for give quotes ' or ". Use following:
<script>
var JSvariable = '<?php echo $PHPvariable; ?>';
//or
var JSvariable = "<?php echo $PHPvariable; ?>";
</script>
Reason: If php variable contains string and if while assigning it to javascript variable we shall not give quote like:
<?php $PHPvariable = 'String';?>
var JSvariable = <?php echo $PHPvariable; ?>;
Will transform into :
var JSvariable = String;//which will give error in javascript
But this will work fine if PHP variable contains a numeric value like:
<?php $PHPvariable = 2;?>
var JSvariable = <?php echo $PHPvariable; ?>;
Will transform into :
var JSvariable = 2;//which will work perfect
Complete code should be:
<script>
var currentreplyid = "<?php echo $allpostcomments[$key]['replyid']; ?>";
//or if you are sure your variable contains int value
var currentreplyid = parseInt("<?php echo $allpostcomments[$key]['replyid']; ?>");
$('#parentcommentholder').val(currentreplyid);
</script>

Try the below instead of using javascript (as I don't think you need it):
<?php
$postcommentsquery = "SELECT * FROM comments WHERE parent = :parent AND postid = :postid ORDER BY datecreated DESC";
$postcommentsparams = array(':parent' => $allreplies[$key]["postid"],
':postid' => $postid);
try{
$postcommentsstmt = $connection->prepare($postcommentsquery);
$postcommentsresult = $postcommentsstmt->execute($postcommentsparams);
}
catch(PDOException $ex){
echo ("Failed to run query: " . $ex->getMessage());
}
$allpostcomments = $postcommentsstmt->fetchAll();
foreach ($allpostcomments as $key => $value) {
?>
<input id="parentcommentholder" value="<?php echo ((int)$allpostcomments[$key]['replyid']>0) ? $allpostcomments[$key]['replyid'] : 0; ?>" />
<?php
}
?>
If your defiantly sure $allpostcomments[$key]['replyid'] is bringing back a value, this should work without any issues.