PHP提交后调用JavaScript函数

Question

I'm trying to figure out why this function isn't being called after the form is submitted. The "checkForm()" JS function works fine when the form is submitted, but I can't seem to get the checkDates() function working. I tried moving it above the PHP code and no alert message showed up. Any help is greatly appreciated, thank you!

Here's the pseudo code version of my file:

<?php

if(isset($_POST['next'])){
    // Some PHP code

    echo "<script> checkDates(); </script>";
}

?>

<form name="form1" id="form1" method="post" action="<?php print $thispage;?>" onsubmit="return checkForm()">

// Some HTML code

</form>

<script>
var isDateTimeValid = true;

function checkDates() {
    alert("Hello");
    isDateTimeValid = false;
}

function checkForm () {

    if (isDateTimeValid == true) {
        return true;
    }
    else {
        return false;
    }
}

</script>

Answer 1

try this it will work.

here your php code must be last in your file then it will work. otherwise not.

     <form name="form1" id="form1" method="post" action="#" onsubmit="return  checkForm()">

     // Some HTML code
     <input type="hidden" name="next" value="sd">
     <input type="submit">

     </form>

     <script>
      var isDateTimeValid = true;

       function checkDates() {
       alert("Hello");
       isDateTimeValid = false;
      }

     console.log(isDateTimeValid);
     function checkForm () {

     if (isDateTimeValid == true) {
        return true;
     }
     else {
        return false;
       }
     }

   </script>
   <?php

    if(isset($_POST['next'])){
      echo "<script> checkDates(); </script>";
     } 
     ?>