A simple PHP class that with 2 main functions: copy an image from a website to the server and resize and crop the image to the specified size.

ImageHelper.php

<?php
/********************************************************************************************/
/* ImageHelper created by Angelo Villegas [http://www.angelovillegas.com]                   */
/*                                                                                          */
/* Copyright © Angelo Villegas                                                              */
/* Permission is hereby granted, free of charge, to any person obtaining a copy of this	    */
/* software and associated documentation files (the "Software"), to deal in the Software    */
/* without restriction, including without limitation the rights to use, copy, modify,	    */
/* merge, publish, distribute, sublicense, and/or sell copies of the Software, and to	    */
/* permit persons to whom the Software is furnished to do so, subject to the following	    */
/* conditions:                                                                              */
/*                                                                                          */
/* The above copyright notice and this permission notice shall be included in all copies    */
/* or substantial portions of the Software.                                                 */
/*                                                                                          */
/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,      */
/* INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A            */
/* PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT	    */
/* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF	    */
/* CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE	    */
/* OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                                            */
/********************************************************************************************/

class ImageHelper
{
    function saveImage( $url = null , $imageURL = null )
    {
        // any can not be null
        if ( is_null( $url ) || is_null( $imageURL ) )
        {
            return false;
        }
        else
        {
            $curl = curl_init( $url ); // initialise curl using the URL
            $file = fopen( $imageURL , 'wb' ); // open the image path, create if it does not exist
            curl_setopt( $curl , CURLOPT_FILE , $file ); // setup the file to be written to
            curl_setopt( $curl , CURLOPT_HEADER , false ); // include header, false if not
            curl_setopt( $curl , CURLOPT_FOLLOWLOCATION , true ); // true to follow any "location" the server sent
            curl_exec( $curl );
            curl_close( $curl );
            fclose( $file );
            
            return true;
        }
    }
    
    function resizeCrop( $image , $savePath = null , $crop = null , $size = null )
    {
        $image = imagecreatefromstring( file_get_contents( $image ) );
        
        if ( is_resource( $image ) === true ) // check if the image is a resource
        {
            $x = 0;
            $y = 0;
            $width = imagesx( $image );
            $height = imagesy( $image );
            
            // crop
            if ( is_null( $crop ) === true ) // check if $crop is null
            {
                $crop = array( $width , $height );
            }
            else
            {
                $crop = array_filter( explode( ':' , $crop ) ); // explode crop ratio
                
                if ( empty( $crop ) === true )
                {
                    $crop = array( $width , $height );
                }
                else
                {
                    // check wether empty or non-numeric
                    if ( ( empty( $crop[0] ) === true ) || ( is_numeric( $crop[0] ) === false ) )
                    {
                        $crop[0] = $crop[1];
                    }
                    else if ( ( empty( $crop[1] ) === true ) || ( is_numeric( $crop[1] ) === false ) )
                    {
                        $crop[1] = $crop[0];
                    }
                }
                
                $ratio = array( 0 => $width / $height , 1 => $crop[0] / $crop[1] ); // initialise ratio
                
                if ( $ratio[0] > $ratio[1] )
                {
                    $width = $height * $ratio[1];
                    $x = ( imagesx ( $image ) - $width ) / 2;
                }
                else if ($ratio[0] < $ratio[1])
                {
                    $height = $width / $ratio[1];
                    $y = ( imagesy( $image ) - $height ) / 2;
                }
            }
            
            // resize
            if ( is_null( $size ) === true ) // check if $size is null
            {
                $size = array( $width , $height );
            }
            else
            {
                $size = array_filter( explode( 'x' , $size ) ); // explode size in pixels
                
                if ( empty( $size ) === true )
                {
                    $size = array( imagesx( $image ) , imagesy( $image ) );
                }
                else
                {
                    if ( ( empty( $size[0] ) === true ) || ( is_numeric( $size[0] ) === false ) )
                    {
                        $size[0] = round( $size[1] * $width / $height );
                    }
                    else if ( ( empty( $size[1] ) === true ) || ( is_numeric( $size[1] ) === false ) )
                    {
                        $size[1] = round( $size[0] * $height / $width );
                    }
                }
            }
            
            // create image
            $result = imagecreatetruecolor( $size[0] , $size[1] );
            
            if ( is_resource( $result ) === true )
            {
                imagesavealpha( $result , true );
                imagealphablending( $result , true );
                imagefill( $result , 0 , 0 , imagecolorallocate( $result , 255 , 255 , 255 ) );
                imagecopyresampled( $result , $image , 0 , 0 , $x , $y , $size[0] , $size[1] , $width , $height );
                
                imageinterlace( $result , true );
                imagejpeg( $result , $savePath , 90 );
                imagedestroy( $result );
            }
        }
        
        return false;
    }
}