Compress svg files in PHP

Question

I wrote something to "compress" svg files. The svg files I am using often have comments and empty <g> tags, and I want to remove them. My main goal is not the speed of the compression, but the size of the compressed svg file.

Here is an example svg file: https://image.flaticon.com/icons/svg/222/222436.svg

And here is the code I am using:

public function compress($svg)
{
 $svg = preg_replace('/<!--.*-->/', '', $svg);
 $svg = preg_replace('/<g>[\n\r\s]*<\/g>/', '', $svg);
 $svg = preg_replace('/\n/', ' ', $svg);
 $svg = preg_replace('/\t/', ' ', $svg);
 $svg = preg_replace('/\s\s+/', ' ', $svg);
 $svg = str_replace('> <', '><', $svg);
 $svg = str_replace(';"', '"', $svg);
 return $svg;
}

1. Do you see any dangers here, perhaps this could ruin some svg files?
2. Is there something I could do to compress the file even more?
3. Is there any way to speed this up?

• hjpotter92: You code does not account for multiline comments (for eg: hastebin.com/idetufocat.xml)

Answer 1

SVG is structured data and should therefore not require regex to work with it. I would suggest that you work with either an XML or SVG-specific library in PHP which would let you parse in the input SVG, remove any unwanted nodes and then render it back out.

Here is a starting point for common PHP tools for working with XML that should be able to do what you want.

This also looks like a library that could meet your needs.