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PHP File Upload

Sure! Let's go through the basics of PHP file upload with an example.

Step-by-Step Guide to PHP File Upload

HTML Form for File Upload Create an HTML form that allows users to select a file to upload.

<!DOCTYPE html>
<html>
<body>

<h2>File Upload Form</h2>
<form action="upload.php" method="post" enctype="multipart/form-data">
  Select file to upload:
  <input type="file" name="fileToUpload" id="fileToUpload">
  <input type="submit" value="Upload File" name="submit">
</form>

</body>
</html>

This form uses the POST method and the enctype="multipart/form-data" attribute, which is necessary for file uploads.

PHP Script to Handle File Upload Create a PHP script (upload.php) that handles the file upload process.

<?php
$target_dir = "uploads/";
$target_file = $target_dir . basename($_FILES["fileToUpload"]["name"]);
$uploadOk = 1;
$imageFileType = strtolower(pathinfo($target_file, PATHINFO_EXTENSION));

// Check if image file is a actual image or fake image
if(isset($_POST["submit"])) {
    $check = getimagesize($_FILES["fileToUpload"]["tmp_name"]);
    if($check !== false) {
        echo "File is an image - " . $check["mime"] . ".";
        $uploadOk = 1;
    } else {
        echo "File is not an image.";
        $uploadOk = 0;
    }
}

// Check if file already exists
if (file_exists($target_file)) {
    echo "Sorry, file already exists.";
    $uploadOk = 0;
}

// Check file size
if ($_FILES["fileToUpload"]["size"] > 500000) {
    echo "Sorry, your file is too large.";
    $uploadOk = 0;
}

// Allow certain file formats
if($imageFileType != "jpg" && $imageFileType != "png" && $imageFileType != "jpeg"
&& $imageFileType != "gif" ) {
    echo "Sorry, only JPG, JPEG, PNG & GIF files are allowed.";
    $uploadOk = 0;
}

// Check if $uploadOk is set to 0 by an error
if ($uploadOk == 0) {
    echo "Sorry, your file was not uploaded.";
// if everything is ok, try to upload file
} else {
    if (move_uploaded_file($_FILES["fileToUpload"]["tmp_name"], $target_file)) {
        echo "The file ". htmlspecialchars( basename( $_FILES["fileToUpload"]["name"])). " has been uploaded.";
    } else {
        echo "Sorry, there was an error uploading your file.";
    }
}
?>

This script performs several checks:

Checks if the uploaded file is an actual image.
Checks if the file already exists in the uploads/ directory.
Checks if the file size is within the limit (500 KB in this case).
Checks if the file type is allowed (JPG, JPEG, PNG, GIF).
If all checks pass, the file is moved to the uploads/ directory.

Explanation of PHP Code

Directory and File Path Setup:

$target_dir = "uploads/";
$target_file = $target_dir . basename($_FILES["fileToUpload"]["name"]);
$uploadOk = 1;
$imageFileType = strtolower(pathinfo($target_file, PATHINFO_EXTENSION));

Check if Image File:

if(isset($_POST["submit"])) {
    $check = getimagesize($_FILES["fileToUpload"]["tmp_name"]);
    if($check !== false) {
        echo "File is an image - " . $check["mime"] . ".";
        $uploadOk = 1;
    } else {
        echo "File is not an image.";
        $uploadOk = 0;
    }
}

Check if File Already Exists:

if (file_exists($target_file)) {
    echo "Sorry, file already exists.";
    $uploadOk = 0;
}

Check File Size:

if ($_FILES["fileToUpload"]["size"] > 500000) {
    echo "Sorry, your file is too large.";
    $uploadOk = 0;
}

Allow Certain File Formats:

if($imageFileType != "jpg" && $imageFileType != "png" && $imageFileType != "jpeg"
&& $imageFileType != "gif" ) {
    echo "Sorry, only JPG, JPEG, PNG & GIF files are allowed.";
    $uploadOk = 0;
}

Upload File if No Errors:

if ($uploadOk == 0) {
    echo "Sorry, your file was not uploaded.";
} else {
    if (move_uploaded_file($_FILES["fileToUpload"]["tmp_name"], $target_file)) {
        echo "The file ". htmlspecialchars( basename( $_FILES["fileToUpload"]["name"])). " has been uploaded.";
    } else {
        echo "Sorry, there was an error uploading your file.";
    }
}

Output

When you run the HTML form and upload a file, you will see messages based on the checks performed:

If the file is not an image:
```
File is not an image.
```
If the file already exists:
```
Sorry, file already exists.
```
If the file is too large:
```
Sorry, your file is too large.
```

If the file format is not allowed:

Sorry, only JPG, JPEG, PNG & GIF files are allowed.

If there is an error uploading the file:

Sorry, there was an error uploading your file.

If the file is successfully uploaded:

The file filename.jpg has been uploaded.

This is a basic example. In a real-world scenario, you might want to add more security checks and handle other possible errors.

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