I was routinely upgrading my packages on Homebrew when I ran into the following error:
$ brew upgrade ==> Upgrading 1 outdated package, with result: homebrew/php/php70 7.0.4 ==> Upgrading homebrew/php/php70 ==> Downloading https://php.net/get/php-7.0.4.tar.bz2/from/this/mirror Already downloaded: /Library/Caches/Homebrew/php70-7.0.4 ==> ./configure --prefix=/usr/local/Cellar/php70/7.0.4 --localstatedir=/usr/local/var --sysconfdir=/usr/local/etc/php/7.0 --with-config-file-path=/usr/local/etc/php/7.0 --wi Last 15 lines from /Users/johnro/Library/Logs/Homebrew/php70/01.configure: checking for OpenSSL support... yes checking for Kerberos support... /usr checking whether to use system default cipher list instead of hardcoded value... no checking for krb5-config... /usr/bin/krb5-config checking for RAND_egd... no checking for pkg-config... no checking for OpenSSL version... >= 0.9.8 checking for CRYPTO_free in -lcrypto... yes checking for SSL_CTX_set_ssl_version in -lssl... yes checking for PCRE library to use... bundled checking whether to enable the SQLite3 extension... yes checking bundled sqlite3 library... yes checking for ZLIB support... yes checking if the location of ZLIB install directory is defined... no configure: error: Cannot find libz
Of course, I did the first thing I always do when running into an error, Google it! And I found this link that suggested running the following:
$ xcode-select --install
After that,
$ brew upgrade
ran fine.