rename image

I am not very experienced in php. I have following problem:

I am uploading a picture and during upload I create a new resized picture. I would like to rename this picture like that:
s_filename.jpg > x_filename.jpg

this script is only setting the x_ as prefix. so I get x_s_filename.jpg, but I need only x_filename.jpg

My script:

PHP Code:

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rename($file, $cfgrow['imagepath'].'x_'.$img_file_name); 


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how can I manage this?

I looking forward for any help!

One way:

PHP Code:

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rename($file, $cfgrow['imagepath'] . substr_replace($img_file_name, 'x_', 0, 2)); 


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Yes, this was very helpful, it is working