composer実行時のUncaught exceptionエラー

いつも通り以下でcomposer入れて〜

curl -s https://getcomposer.org/installer | php

応答

#!/usr/bin/env php
All settings correct for using Composer
Downloading...

Composer successfully installed to: /Users/mymac/Sites/composer.phar
Use it: php composer.phar

ちゃんと入ったっぽいのにいざ実行してみると

php composer.phar

以下のエラー。

PHP Fatal error:  Uncaught exception 'PharException' with message 'phar "/Users/mymac/Sites/composer.phar" has a broken signature' in /Users/mymac/Sites/composer.phar:22
Stack trace:
#0 /Users/mymac/Sites/composer.phar(22): Phar::mapPhar('composer.phar')
#1 {main}
  thrown in /Users/mymac/Sites/composer.phar on line 22

Fatal error: Uncaught exception 'PharException' with message 'phar "/Users/mymac/Sites/composer.phar" has a broken signature' in /Users/mymac/Sites/composer.phar on line 22

PharException: phar "/Users/mymac/Sites/vcomposer.phar" has a broken signature in /Users/mymac/Sites/composer.phar on line 22

Call Stack:
    0.0006     228272   1. {main}() /Users/mymac/Sites/composer.phar:0
    0.0006     228368   2. Phar::mapPhar() /Users/mymac/Sites/composer.phar:22

原因は分かりません。
もう一回、

curl -s https://getcomposer.org/installer | php

からやり直すと治ります。
ファイルが壊れてたのかも。