$re = '/,{"author[^*]*],\s*/m';
$str = 'json_file<- \'{"_id":{"$oid":"4f27779008d69a6dba0208f6"},"actor":{"gravatar_id":"92e5c51218f00220e0362c47b2a94b9a","id":NumberInt(228889),"login":"stefankendall","url":"https://api.github.com/users/stefankendall"},"created_at":"2012-01-31T05:09:37Z","id":"1515677813","org":{"url":"https://api.github.com/orgs/"},"payload":{"commits":[{"author":{"email":"skendall@skendalllaptop.(none)","name":"skendall"},"message":"Made test packages mimic app layout.","sha":"faf1b478f4d98202d4169b6d310812b14ad7f676","url":"https://api.github.com/repos/stefankendall/wendler531-webservices/commits/faf1b478f4d98202d4169b6d310812b14ad7f676"},{"author":{"email":"skendall@skendalllaptop.(none)","name":"skendall"},"message":"_id is now pulled out of \\"get\\" responses","sha":"d2087821e865ebebf9ff6e47cffb41dd16c6c871","url":"https://api.github.com/repos/stefankendall/wendler531-webservices/commits/d2087821e865ebebf9ff6e47cffb41dd16c6c871"}],"head":"d2087821e865ebebf9ff6e47cffb41dd16c6c871","push_id":NumberInt(59920001),"ref":"refs/heads/master","size":NumberInt(2)},"public":true,"repo":{"id":NumberInt(3186494),"name":"stefankendall/wendler531-webservices","url":"https://api.github.com/repos/stefankendall/wendler531-webservices"},"type":"PushEvent"}\'
';
$subst = "";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php