Extension Possibilities
As shown in Figure 9.1 above, PHP can be extended primarily at three points: external modules, built-in modules, and the Zend engine. The following sections discuss these options.
External Modules
External modules can be loaded at script runtime using the function dl(). This function loads a shared object from disk and makes its functionality available to the script to which it's being bound. After the script is terminated, the external module is discarded from memory. This method has both advantages and disadvantages, as described in the following table:
| Advantages | Disadvantages |
|---|---|
| External modules don't require recompiling of PHP. | The shared objects need to be loaded every time a script is being executed (every hit), which ... |
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