Fit text of any length into image of fixed dimensions

It's interesting: fitting text like this is one of those problems which I've found beginner programmers often struggle with when they come up against it. It really doesn't seem like it should be as hard as it is. Latin characters - go figure.

> $command = 'convert -page +5+5 -background "#'.$bgcolor.'" -fill "#000000" -font '.$font.' -size 310x680 caption:"'.$text.'" -page +0+695 -background "#000000" -fill "#000000" -size 320x60 caption:"-" -page +3+708 -background "#000000" -fill "#FFFFFF" -font '.$font.' -size 310x44 caption:"www.CORRELATED.org /'.$blog_id.'" -background "#'.$bgcolor.'" -layers mosaic pinterest_'.$blog_id.'.jpg

There should be a whole bunch of escapeshellarg() in there. Who knows what the text contains? Code like this is exactly why PHP devs get a bad rep. Please don't post PHP code online unless you've made it reasonably secure, because somebody somewhere is going to copy that and get pwned.

Also, why not use PHP's own imagick extension? It exposes a neat object-oriented interface, it will be much easier for people to read and tweak, and you won't have to escape anything.