Just output a warning but don't prevent usage through non-cli SAPIs
merged branch jsor/php-sapi-warning (PR #80)

This PR was merged into the master branch.

Discussion
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Just output a warning but don't prevent usage through non-cli SAPIs

Composer has also turned this into a warning in composer/composer@c1ff6ea62bb2c196e777bcd51ac6da287ad44b5a

Commits
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24541e0 Just output a warning but don't prevent usage through non-cli SAPIs