How to stop Subversion from prompting about: Server certificate verification failed: issuer is not trusted

I need to be able to deploy new instances of an application from a subversion repository. This is accomplished by running shell_exec() from a PHP script.

However, Subversion won't let me check out the repository, instead throwing this error:

svn: OPTIONS of 'https://www.example.org/svn/repos/project/trunk': Server certificate verification failed: issuer is not trusted (https://www.example.org)

How can I get Subversion to let me check out the code and ignore the certificate error? If I check it out from an SSH session it prompts and and caches the certificate and works fine the second time. When run via the PHP script, however, it never works.

From the svn help file under the global options section svn help checkout

  --non-interactive        : do no interactive prompting
  --trust-server-cert      : accept unknown SSL server certificates without
                             prompting (but only with '--non-interactive')

should do what you need.