Prior to version 4.3 of Xcode, Apple bundled a load of command line tools with it that are used to compile native binaries, including PHP extensions. However, as of version 4.3, these tools are not bundled by default. Therefore, if you require these tools you need to take one of two actions:
1. If you already have Xcode 4.3 installed, go into the Components tab of the Download preferences panel and make sure Command Line Tools are selected
2. Download and install the command line tools as an independent package from either;
Once you have the command line tools installed, you are able to compile native binaries.
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