The performance of PHP and Java can depend on a variety of factors, including the specific implementation, the hardware and software environment, and the workload of the application.

In general, Java is considered to be a faster and more efficient language than PHP. Java's performance benefits from the fact that it is a compiled language, which means that it is translated into machine code at compile time. This results in faster execution times and better memory management.

On the other hand, PHP is an interpreted language, which means that it is executed on the fly by the PHP interpreter. This can result in slower execution times and less efficient memory management.

However, it's important to note that the performance of PHP can be optimized by using various techniques such as opcode caching, which caches compiled bytecode to avoid the overhead of recompiling the same code on each request. Additionally, PHP has a number of performance tuning options and extensions that can be used to optimize performance.

Here is an example of a performance comparison between PHP and Java for a specific use case:

Let's say we have a web application that needs to handle a high volume of concurrent requests and perform complex calculations on each request. We could implement this application in both PHP and Java and compare their performance.

For the PHP implementation, we might use the popular web application framework Laravel, which provides a range of features and tools for building web applications. We might also use the OPCache extension, which caches compiled PHP bytecode to speed up execution times.

For the Java implementation, we might use the Spring Framework, which provides a range of features for building enterprise-scale web applications. We might also use the JIT compiler, which compiles Java bytecode to machine code at runtime for faster execution.

To compare the performance of the two implementations, we might measure the response time and throughput of the application under varying loads. We might also measure memory usage and CPU utilization to evaluate the efficiency of each implementation.

In general, we might expect the Java implementation to perform better under high load and for complex calculations due to its compiled nature and better memory management. However, the PHP implementation may be more lightweight and easier to develop due to its interpreted nature and the availability of many frameworks and tools.

Ultimately, the performance of PHP and Java can vary depending on the specific use case and implementation, so it's important to evaluate each on a case-by-case basis.