PHP Fatal error: Call to undefined function: mail()

Or: "How to fix this weird (and frustrating) error"


So, we got this weird (and frustrating) error on our production server and I didn't find much help on Google at the time. We got to fix it, so now is the time to give back.

Executive summary: This error occurs because PHP couldn't find sendmail at compile time. So the mail function didn't get built, thank you. Here's what to do to fix it:

  • If you compiled PHP before compiling (or installing) Sendmail, you just have to recompile PHP again (with Sendmail installed) and, hopefully, you're done.
  • If you use QMail (that was our case), you have to fool PHP that Sendmail is actually there, using QMail's wrapper. Just do: ln -s /var/qmail/bin/sendmail /usr/sbin/sendmail , recompile and, hopefully, you're done.
  • You're using some other esoteric mail server which is not Sendmail. If it has a wrapper to Sendmail, try the QMail tip (doing a symbolic link to the wrapper). If you don't have a wrapper, well... you're on your own. Unless you really need to use that mail server, I recommend QMail or Postfix.

    • In all cases you must recompile. It's important to do a make clean and then do the whole configure/make/make install dance, otherwise you'll compile the same configuration (with no mail function) all over again. Yes, I did that twice, silly me.

    I don't know exactly in which places PHP looks for Sendmail, but I know one of them is /usr/sbin/ (to make it clear, it looks for the file /usr/sbin/sendmail).

    Hope that helps.

    Revisions:
    2004/01/13 - Thanks to Oliver for pointing an incorrect ln call. It's fixed now.

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