php resize image on upload
$maxDim = 800;
$file_name = $_FILES['myFile']['tmp_name'];
list($width, $height, $type, $attr) = getimagesize( $file_name );
if ( $width > $maxDim || $height > $maxDim ) {
$target_filename = $file_name;
$ratio = $width/$height;
if( $ratio > 1) {
$new_width = $maxDim;
$new_height = $maxDim/$ratio;
} else {
$new_width = $maxDim*$ratio;
$new_height = $maxDim;
}
$src = imagecreatefromstring( file_get_contents( $file_name ) );
$dst = imagecreatetruecolor( $new_width, $new_height );
imagecopyresampled( $dst, $src, 0, 0, 0, 0, $new_width, $new_height, $width, $height );
imagedestroy( $src );
imagepng( $dst, $target_filename ); // adjust format as needed
imagedestroy( $dst );
}