ho risolto solamente perchè devo fare la miniatura quadrata se a qualcuno servo ho fatto così:

Codice PHP:
$ima=$_SESSION['upload']['percorso'].$file_upload_name;
    
$perc=$_SESSION['upload']['percorso'];
    list(
$width$height) = getimagesize($ima);
    
    
$targ_w 96;
    
$targ_h 96;
    
$jpeg_quality 90;        
    
$src $ima;        
    
//allerta($src);        
    
$img_r imagecreatefromjpeg($src);
    
$dst_r imagecreatetruecolor($targ_w,$targ_h);        
    list(
$w,$h) = getimagesize($src);        
    
    
$source_x=$source_y=0;
    
    if (
$width $height) { $dst_x=$dst_y=$height; } 
    if (
$height $width) { $dst_x=$dst_y=$width; }
    if (
$height == $width) { $dst_x=$dst_y=$height; }
            
    
imagecopyresampled($dst_r,$img_r,0,0,$source_x$source_y,$targ_w,$targ_h,$dst_x,$dst_y);
    
imagejpeg$dst_r$perc."thumb_".$file_upload_name$jpeg_quality );
    
imagedestroy$img_r );
    
imagedestroy$dst_r );