MAC brew install php70

➜  ~  php7 -v
dyld: Library not loaded: /usr/local/lib/libpng16.16.dylib
  Referenced from: /usr/bin/php7
  Reason: image not found
[1]    95671 trace trap  php7 -v

how to solve this problem？

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➜ ~ brew install php56
Error: You must `brew link libpng unixodbc' before homebrew/php/php56 can be installed

➜ ~ brew link libpng unixodbc
Error: Could not symlink share/man/man5/png.5
/usr/local/share/man/man5 is not writable.

➜ man git:(master) ll
total 8
drwxr-xr-x 55 Yugo admin 1.8K 10 12 23:06 man1
drwxr-xr-x 103 Yugo admin 3.4K 10 13 18:10 man3
drwxr-xr-x 4 root wheel 136B 1 6 2015 man5
drwxr-xr-x 6 root admin 204B 8 24 19:33 man8
drwxr-xr-x 6 root wheel 204B 3 30 2013 mann
-rw-r--r-- 1 root admin 3.9K 10 12 13:59 whatis

➜ man git:(master) sudo chmod 777 man5

➜ man git:(master) brew link libpng unixodbc
Linking /usr/local/Cellar/libpng/1.6.18... 18 symlinks created
Linking /usr/local/Cellar/unixodbc/2.3.2_1... 28 symlinks created