Your comments

Thanks for the detailed description.

I tried to reproduce it but as you can see in the screenshot below it works for me as it should. Also, I could replace " dog" with " cat".

I spent the evening optimizing the start-up time of Textastic. For me it is now about twice as fast. On my iPad 2 the app launches in about 4 seconds now. This optimization will be available in the next update.
I hope I can improve performance by loading the syntax definitions when they are needed instead of at application startup.

Just to make sure there isn't another problem: are you using and iPad 1 or 2? Can you give me an estimate, how long it takes to launch the app?
Um PHP-Fehler anzuzeigen, müsste Textastic einen PHP-Interpreter mitliefern oder die Daten an einen Online-Dienst schicken. Ich werde mir überlegen, ob das vielleicht in einer zukünftigen Version umzusetzen ist.

Das Einstellen der Sonderzeichen wird in einer der nächsten Versionen kommen.
Textastic loads all syntax definitions on startup. I have already optimized the startup speed but I hope to further improve this in the future. I don't think there's anything you can do about it.
Maybe it's a tab character instead of space? You can search for tabs with "\t" and for newlines with "\n".

You can also change the tab width in settings.
Hello,

I just tried it out and it does work for me. Textastic does correctly replace two spaces. I also searched for a space and a word and it also found it.

Maybe you can give me some more details how your file looks and what exactly you searched for. 
Textastic supports TextExpander touch. This allows you to create custom snippets: http://www.smilesoftware.com/TextExpander/touch/
Can't you open it at all or is there just no syntax highlighting?
Hi, minified files are basically just one line of code. If you change one character in this line, Textastic has to highlight and relayout this line due to how the syntax highlighter works.

I don't recommend editing minified files with Textastic.