Does Pass-by-Reference Offer Performance Benefits in PHP?

Pass-by-Reference: Any Performance Benefits in PHP?

In PHP, passing parameters by reference can be achieved by prepending an ampersand to the parameter in the function declaration. While this primarily serves to enable functions to modify variables outside their scope, speculation has arisen regarding potential performance enhancements.

However, detailed testing reveals that passing parameters by value actually yields faster results, both when the function merely reads or uses the parameter and when it modifies its value.

Benchmarks

Tests involving 100,000 iterations of calling a function with a string of 20 kB demonstrate the following performance differences:

Reading / Using the Parameter

• Pass by value: 0.12065005 seconds
• Pass by reference: 1.52171397 seconds

Writing / Changing the Parameter

• Pass by value: 1.52223396 seconds
• Pass by reference: 1.52388787 seconds

Conclusions

1. Passing parameters by value consistently performs faster in PHP.
2. For functions that modify passed parameter values, the performance impact between passing by value and reference is negligible.

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