composer php - Could not parse version constraint ~x.x: Invalid version string "~x.x" -

i downloaded composer.phar with:

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

then run command:

php composer.phar require mailgun/mailgun-php:~x.x 

but got error:

[unexpectedvalueexception]
not parse version constraint ~x.x: invalid version string "~x.x"

searching internet, responses update latest composer.phar. downloaded it. if case, how update? (this on mac os x ver 10.10.5)

in version constraints, x means any number. any number.any number in other words: me random release.

~1.2 means >=1.2,<2.0. in more formal way: ~y.z means >=y.z,<(y+1).0.

what give me @ least release, lower release + 1. of course not resolvable. if was, it's highly dangerous allow releases.

so have change version constraint better or more secure. instance, if want 1.x release, use 1.x, 1.* or ~1.0. if want 1.x release or 2.x release, use 1.x|2.x or other variant mentioned before.

for more information version constraints, read composer documentation. see usefull version constraint tester test version constraints.