Trigger JQuery function based on value of variable - php

Question

I have a page that receives incoming values from $_POST. One such value is from a drop down selector that allowed the user to select values 0 -10. I want to trigger a JQuery function if a value greater than 0 was selected.
So, if $_POST['DropDownSelection'] > 0, then my JQuery function should run.
How do I trigger the function?

Answer 1

If the function needs to be called in the original page then you can do this -
$('select[name="DropDownSelection"]').change(function() {
var newValue = $(this).val();
if(newValue > 0) {
// your function here
}
});
You don't need PHP, you just need to see if the value changed and then if the value is greater than 0.
If the function is in the page that gets posted to then you could do this -
<script>
var DropDownSelection = <?php echo $_POST['DropDownSelection']; ?>;
if(DropDownSelection > 0) {
// call your function here
}
</script>

Answer 2

Something i like to do for passing a PHP var to Javascript is to put in in an hidden input like that :
<input id="myValue" type="hidden" value="<?= $_POST['DropDownSelection']; ?>" />
The in your javascript :
if(document.getElementById('myValue').value > 0) //Do something

Answer 3

Depends on how your PHP code is connected to the HTML output. In the simplest case where PHP and HTML are in the same file, you could do something like
<? if ($_POST['DropDownSelection'] > 0) { ?>
<script>$.myFunction(...);</script>
<? } ?>

Answer 4

You can do like that.
var x = <?php echo $_POST['DropDownSelection'] ?>;
if(x>0){
jqueryFunction(); // your function call.
}else{
// whatever else you want.
}

Answer 5

Maybe this is oversimplified and a little hacky, but I don't see why this wouldn't work...
<script type="text/javascript">
function overZero() {
// do stuff...
}
<?php
if ($_POST['DropDownSelection']>0) echo('overZero();');
?>
</script>

Answer 6

$(document).ready(function(){
$("#dropdown-id").change(function(){
//check if the value is > 0 and then
// trigger your jquery function()
})
})

Answer 7

However, I want to also call that function when the user lands on the page with
a particular $_POST value for a field
There are 2 easy ways of doing this:
Make global funciton:
ex:
function print(){
alert('hello')
}
<?php
if($_POST['DropDownSelection'] != 0)
{
echo "<script>print()</script>";
}
?>
Or use triger function from jquery:
<?php
if($_POST['DropDownSelection'] != 0)
{
echo "<script>$('#dropdown').trigger('change');</script>";// execute the onchange event(function) attached to the dropdown
}
?>