對於非唯一值搜索，isset 比 in_array 更快嗎？

Which Is Faster: In_array or Isset?

When optimizing code to run efficiently on cost-effective servers or amid high traffic, it's crucial to choose the most performant methods. This comparison explores the speed differences between in_array and isset when searching for non-unique values in an array.

Isset outperforms in_array in this scenario due to several reasons:

1. It utilizes an O(1) hash search, checking the existence of the key directly. In contrast, in_array performs a sequential search, iterating through each value.
2. Isset is an opcode, which incurs less overhead compared to the in_array built-in function.

To illustrate this difference, a benchmark with an array of 10,000 values was conducted:

isset:    0.009623
in_array: 1.738441

This result demonstrates the significant performance advantage of isset over in_array when searching for non-unique values.

Moreover, a customized benchmark, which filled random values into an array of 10,000 elements and occasionally searched for existing values, confirmed the superior performance of isset:

Size: 10000
Total time: 0.051278
Total time: 1.740182

In conclusion, when searching for non-unique values in an array, isset offers a clear speed advantage over in_array, providing greater efficiency and optimized performance.

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