An attachment (also known as a built-in extension ) is a way to optimize a program by replacing function calls with the actual body of the called function at compile time.
It reduces part of the overhead associated with function calls and returns, and in some cases (I'm not sure if PHP is one of them) may allow compilation to further optimize the area of the code after embedding, for example, by removing code that has no effect .
The main drawback that allows the compiler to perform the built-in extension is an increase in the size of the code, which can be significant, given that the call to one function is replaced by all the code of the called function.
Enabling this configuration option will result in potentially faster php scripts with a larger file size.
user622367
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