不在页面加载上运行警报

Question

I have this upload code copy pasted from w3 for image upload and included in a page. The problem is, when the page gets loaded for the first time all the alert boxes get triggered and run. I think the problem is probably because of the $uploadok being not ==. But how do I solve this issue so the alert do not run on start.

I'm actually a beginner so its kinda confusing to come with new logics.

So here is the code

<?php
session_start();
$path = "C:\wamp64\www\Allian\users/".$_SESSION['username']."/uploads";
if (!file_exists($path)) {
    mkdir($path, 0700);
}
$target_dir = "users/".$_SESSION['username']."\uploads/";
$target_file = $target_dir . basename($_FILES["dp_btn"]["name"]);
$uploadOk = 1;
$imageFileType = strtolower(pathinfo($target_file,PATHINFO_EXTENSION));
// Check if image file is a actual image or fake image
if($_SERVER["REQUEST_METHOD"]=="POST") {
  if(isset($_POST["btn_save_changes"])) {
    $check = getimagesize($_FILES["dp_btn"]["tmp_name"]);
    if($check !== false) {
      echo "<script>alert('File is an image - " . $check["mime"] . ".')</script>";
      $uploadOk = 1;
    } else {
        echo "<script>alert('File is not an image.')</script>";
        $uploadOk = 0;
      }
  }
}
// Check if file already exists
if (file_exists($target_file)) {
  echo "<script>alert('Sorry, file already exists.')</script>";
  $uploadOk = 0;
}
// Check file size
if ($_FILES["dp_btn"]["size"] > 500000) {
  echo "<script>alert('Sorry, your file is too large.')</script>";
  $uploadOk = 0;
}
// Allow certain file formats
if($imageFileType != "jpg" && $imageFileType != "png" && $imageFileType != "jpeg"
&& $imageFileType != "gif" ) {
  echo "<script>alert('Sorry, only JPG, JPEG, PNG & GIF files are allowed.')</script>";
  $uploadOk = 0;
}
// Check if $uploadOk is set to 0 by an error
if ($uploadOk == 0) {
  echo "<script>alert('Sorry, your file was not uploaded.')</script>";
// if everything is ok, try to upload file
} else {
    if (move_uploaded_file($_FILES["dp_btn"]["tmp_name"], $target_file)) {
    echo "<script>alert('The file ". basename( $_FILES["dp_btn"]["name"]). " has been uploaded.')</script>";
  } else {
      echo "<script>alert('Sorry, there was an error uploading your file.')</script>";
    }
  }
?>

Thnx

Answer 1

Put everything that you don't want to run on the first page load inside the if(isset($_POST["btn_save_changes"])) { block. That will ensure it only runs on postback and that the "save changes" button was pressed. When you first load the page in your browser it's always done via a GET. POST is only used when you submit a form. Unless the demo you copied from was faulty, I'm surprised it didn't do it like that already.

<?php
session_start();
$path = "C:\wamp64\www\Allian\users/".$_SESSION['username']."/uploads";
if (!file_exists($path)) {
    mkdir($path, 0700);
}
$target_dir = "users/".$_SESSION['username']."\uploads/";
$target_file = $target_dir . basename($_FILES["dp_btn"]["name"]);
$uploadOk = 1;
$imageFileType = strtolower(pathinfo($target_file,PATHINFO_EXTENSION));

// Check if image file is a actual image or fake image
if($_SERVER["REQUEST_METHOD"]=="POST") {
  if(isset($_POST["btn_save_changes"])) {
    $check = getimagesize($_FILES["dp_btn"]["tmp_name"]);
    if($check !== false) {
      echo "<script>alert('File is an image - " . $check["mime"] . ".')</script>";
      $uploadOk = 1;
    } else {
        echo "<script>alert('File is not an image.')</script>";
        $uploadOk = 0;
    }
    // Check if file already exists
    if (file_exists($target_file)) {
      echo "<script>alert('Sorry, file already exists.')</script>";
      $uploadOk = 0;
    }
    // Check file size
    if ($_FILES["dp_btn"]["size"] > 500000) {
      echo "<script>alert('Sorry, your file is too large.')</script>";
      $uploadOk = 0;
    }
    // Allow certain file formats
    if($imageFileType != "jpg" && $imageFileType != "png" && $imageFileType != "jpeg" && $imageFileType != "gif" ) {
      echo "<script>alert('Sorry, only JPG, JPEG, PNG & GIF files are allowed.')</script>";
      $uploadOk = 0;
    }
    // Check if $uploadOk is set to 0 by an error
    if ($uploadOk == 0) {
      echo "<script>alert('Sorry, your file was not uploaded.')</script>";
      // if everything is ok, try to upload file
    } else {
      if (move_uploaded_file($_FILES["dp_btn"]["tmp_name"], $target_file)) {
       echo "<script>alert('The file ". basename( $_FILES["dp_btn"]["name"]). " has been uploaded.')</script>";
        } else {
            echo "<script>alert('Sorry, there was an error uploading your file.')</script>";
        }
    }
  }
}
?>

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P.S. Just an aside: As a user experience, receiving a series of different popups in sequence containing error messages is not a particularly helpful one. They require dismissing one by one which is tedious, and the user might not remember what was in the earlier ones to be able to act on it. You'll find very few modern websites display errors in this way (if any). A much better way would be to build up a HTML list containing all the error messages and then just echo that into a suitable location in the page, where it's visible, and the user can see everything at once whilst trying to correct and re-submit the form..