codice:
<?php

function img2big($src,$alt=NULL)
{

// Constants
define(IMAGE_BASE, 'http://0x010.isf.it');
define(MAX_WIDTH, 150);
define(MAX_HEIGHT, 150);

// Get image location
$image_file = str_replace('..', '', $_SERVER['QUERY_STRING']);
$image_path = IMAGE_BASE . "/$src";


// Load image
$img = null;
$ext = strtolower(end(explode('.', $image_path)));
if ($ext == 'jpg' || $ext == 'jpeg') {
    $img = @imagecreatefromjpeg($image_path);
} else if ($ext == 'png') {
    $img = @imagecreatefrompng($image_path);
// Only if your version of GD includes GIF support
} else if ($ext == 'gif') {
    $img = @imagecreatefrompng($image_path);
}

// If an image was successfully loaded, test the image for size
if ($img) {

    // Get image size and scale ratio
    $width = imagesx($img);
    $height = imagesy($img);
    $scale = min(MAX_WIDTH/$width, MAX_HEIGHT/$height);

    // If the image is larger than the max shrink it
    if ($scale < 1) {
        $new_width = floor($scale*$width);
        $new_height = floor($scale*$height);

        // Create a new temporary image
        $tmp_img = imagecreatetruecolor($new_width, $new_height);

        // Copy and resize old image into new image
        imagecopyresized($tmp_img, $img, 0, 0, 0, 0, 
                         $new_width, $new_height, $width, $height);
        imagedestroy($img);
        $img = $tmp_img;        
    }    
}

// Create error image if necessary
if (!$img) {
    $img = imagecreate(MAX_WIDTH, MAX_HEIGHT);
    imagecolorallocate($img,0,0,0);
    $c = imagecolorallocate($img,70,70,70);
    imageline($img,0,0,MAX_WIDTH,MAX_HEIGHT,$c2);
    imageline($img,MAX_WIDTH,0,0,MAX_HEIGHT,$c2);
}

// Display the image
header("Content-type: image/jpeg");
imagejpeg($img);

//echo "<img src=\"$img\" alt=\"$alt\" />";
}


?>

sembra tutto ok, ma perchè mi da errore:

Warning: Cannot modify header information - headers already sent by (output started at /home/[io]/public_html/alexindex.php:2) in /home/[io]/public_html/funcs.php on line 62

??

Qualcuno mi aiuta??