<?php
	//Open directory
	$dir = opendir('directoryname');
	
	//Start loop for image resize
	while ($file = readdir($dir)) 
	{
		
		//Open Image
		$image = open_image($file);
		if ($image === false) { die ('Unable to open image'); }
		
		// Get original width and height
		$width = imagesx($image);
		$height = imagesy($image);
		
		//Resize image if width over 750
		if ($width > 750) 
		{
			$new_width = 750;
			$old_image = "$dir" . "/" . "$file";
			
			$new_height = $height * ($new_width/$width);
			$image_resized = imagecreatetruecolor($new_width, $new_height);
			imagecopyresampled($image_resized, $image, 0, 0, 0, 0,
								 $new_width, $new_height, $width, $height);
			$ext = strtolower(end(explode(".",$file)));
			if($ext == "jpg" || $ext == "jpeg")
				imagejpeg($image_resized($old_image);
			if($ext == "gif")
				imagegif($image_resized($old_image);
			if($ext == "png")
				imagepng($image_resized($old_image);
		
		}
	}
	
	//Close directory
	closedir($dir);
?>