How can I count all the lines of code in a directory recursively?

For another one-liner:

( find ./ -name '*.php' -print0 | xargs -0 cat ) | wc -l

It works on names with spaces and only outputs one number.

You can use the cloc utility which is built for this exact purpose. It reports each the amount of lines in each language, together with how many of them are comments, etc. CLOC is available on Linux, Mac and Windows.

Usage and output example:

$ cloc --exclude-lang=DTD,Lua,make,Python .
    2570 text files.
    2200 unique files.
    8654 files ignored.

http://cloc.sourceforge.net v 1.53  T=8.0 s (202.4 files/s, 99198.6 lines/s)
-------------------------------------------------------------------------------
Language                     files          blank        comment           code
-------------------------------------------------------------------------------
JavaScript                    1506          77848         212000         366495
CSS                             56           9671          20147          87695
HTML                            51           1409            151           7480
XML                              6           3088           1383           6222
-------------------------------------------------------------------------------
SUM:                          1619          92016         233681         467892
-------------------------------------------------------------------------------

Try:

find . -name '*.php' | xargs wc -l

or (when file names include special characters such as spaces)

find . -name '*.php' | sed 's/.*/"&"/' | xargs  wc -l

The SLOCCount tool may help as well.

It will give an accurate source lines of code count for whatever hierarchy you point it at, as well as some additional stats.

Sorted output:

find . -name '*.php' | xargs wc -l | sort -nr