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Can someone help me understand whether PHP is compiled or interpreted?
I googled it and was left very confused.
It sounds like PHP is compiled to some type of bytecode. But, I have never seen another file created (an executable).
I can't imagine PHP would re-compile each script.php every time it is used, but I don't see any .exe files getting created.
Anyone know how PHP really works? It seems like almost no one knows.
Thanks.
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There is not a clear, absolute distinction. Old style interpreters would interpret the statements of a loop from source code on every iteration of the loop, and similar with other constructs.
To speed up execution, interpreters began (at least 25 years ago, maybe earlier) when analyzing a statement, to leave the analysis in a memory cache. So for a loop, the analysis was done the first time through. Following iterations skipped the analysis step, and rather picked up the analysis from the cache.
As this became more common, the analysis results became more formalized into some variant of P-code, suitable for direct interpretation. When done as a separate step, for an entire program or program module (e.g. the classic Pascal compiler from ETH Zürich), it is always called a compiler. So when the php runtime system does the same thing for a loop, you might say that it is a compiler, compiling that loop.
Another change over time: The first interpreters to save analysis results for later use did it line by line, or statement by statement. More recent interpreters compile larger units, e.g. a complete method, in order to apply optimizations such as moving invariants out of loops, calculating common expressions once only etc.
If the generated code follows a well defined grammar, the runtime compiler may save it to a file or cache. Compare it to dotNet: The IL code(*) of an assembly is compiled to binary machine code by the "jitter" (Just In Time compiler) first time it is run. The jitter also saves the binary code in a (persistent) disk cache that is usually not seen by neither programmer nor user; it is in a file space managed by the jitter alone. Next time the same assembly is run, the jitter first looks in its cache: If an already compiled version is found there, it is loaded, and the JIT compiling is bypassed.
A similar (persistent) caching (of P-code) might be employed by an interpreter. It should not affect the source language - the same source may be interpreted on one machine, compiled to P-code on the fly on every execution on another machine, while a third machine may have an interpreter looking in its cache for an already compiled variant.
This may be applied to a lot of different languages: You could make an interpreter to P-code on the fly, for subsequent immediate interpretation by an interpreter. Usually, you think of Java as a compiled language, but if you integrate JVM with the compiler, they might appear externally just as 'interpreted' as, say, PHP.
(*) dotNet IL code and P-code are at comparable abstraction level. The difference is that P-code is designed to be directly interpreted by a virtual machine; it is complete and ready for running, like a binary machine code (although not the machine code of the real machine you are running). IL code has a lot more 'loose ends' that must be tied up; there are more final decisions to be taken, but then there is more freedom when generating final binary machine code for that specific real machine. You cannot move this binary code to another machine; it may have a CPU missing a few instruction set options (the jitter makes binary code to make use of anything that is available), or maybe a completely different binary instruction set. P-code (usually) can be moved to other machines of arbitrary architecture and instruction set.
Note that P-code (or bytecode) is not a single firmly defined format. There are different P-codes, Java bytecode is not identical to the classical Pascal P4-code (although it is said to be heavily inspired by P4).
Religious freedom is the freedom to say that two plus two make five.
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Sorry, why atre you telling me this?
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Because a public post is intended for the entire reading audience, not just for you alone.
I wrote my post to expand on your WDYJFGI style reply; that is why it came as a follow up to yours.
I had a coworker who was a real nuisance in informal conversations: All the time he interrupted "You have told that earlier!", and I had to reply: "Yes, to you, but this was John asking, and he hasn't heard it yet!" This guy never learned; it happened again and again.
For some reason, your reply/question made me think of this fellow.
Religious freedom is the freedom to say that two plus two make five.
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Well maybe so, but it would have been better posted in reply to the question, as the OP is the one asking for the information. I suspect that very few people will actually read your response as it does not appear to be an answer to the question.
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PHP is a scripting language, which basically means there is an "exe" somewhere reading the php script every time there is a request.
For php that will be Zend Engine.
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I'm working on a web development project and I'm struggling with optimizing performance for my website. Are there any best practices or specific techniques that developers recommend to improve website speed and performance, especially when dealing with large amounts of data or complex interactions?
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That is such a broad question, I can only assume this is a setup for a "search engine optimisation" spammer to respond with an advert for their services.
If that wasn't your intention, then you need to provide a lot more information about your specific problem, what you have tried, and where you are stuck.
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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The question is indeed broad but one could start off with Lighthouse audit if being completely new to this. It provides a nice set of rules for web projects.
However, gaining some experience I would advise applying more of system thinking. I.e. identifying the exact bottleneck (i.e slow backend or excessive javascript bundle size) via developer tools and fixing it.
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When dealing with large amounts of data, try to use caching instead of going to database for every request.
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how to upload a pdf in mern project
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Doing lots of web work in my current job...
We got a legacy solution (though still in use) which has ASP.NET/.NET4.8 Web projects in it.
Unfortunately, looking at it today (with VS 17.8.2, if it's of any relevance - i.e. latest one with the .net8 bits) and... I can't get any breakpoint to work! 
I wonder... If anyone else here experiences the same misfortune? or has any idea?
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Did you post the correct link? Or report the problem in the OP correctly?
The link suggests a problem with viewing a value. The OP suggests a problem with setting the break point (just that.)
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my boss sent me this link and it seemed to be only vaguely related... but the 3rd last post suggested what solved it for us apparently, to add that in the .csproj,
<DebugType>portable</DebugType>
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I am primarily a test automation engineer, and I have very little experience with full-stack Web development, but I'd like to learn. I have an idea for a training/education video platform in the vein of Pluralsite or Udemy but tailored for college-level instructors and their students.
A professor creates accounts for his/her students, and when the students log in they are directed to a page with links to tutorial/instructional videos relevant to the course. The video player is set up in such a way that the student can't fast forward, only pause or rewind or scroll up to the video's current elapsed time. After the student reaches the end of the video, he/she can scroll the entire length of the tutorial (permanently) and unlocks the next video in the series. The idea is that the student can earn a participation grade by watching the tutorials from beginning to end and can't "cheat" just by scrolling to the end.
The tutorials will be interrupted randomly with video clips displaying questions which will appear on an upcoming exam, kind of like YouTube ads you can skip after a few seconds. Every question on a given exam will show up, but not every question will appear to every student. The students are therefore incentivized to watch every video so as to gather test questions then work together with their peers to prepare for the test.
I believe this could be a useful tool for teachers who can't fit all the material they're required to cover in a single 55 minute lecture. For example, a computer science instructor could use the lecture to discuss concepts and theory and then use the tutorial system to demonstrate how to code.
I'd like some advice on how to get started. Has anyone already done something like this? What's a good framework to build the UI? What about the backend? I have some experience with React.js and C# ASP.NET.
Can anyone recommend any good tutorials for this sort of project?
Here's a big one: are there any open-source tools I can use to build mock-ups of web pages? Can I use an open-source video player, or would I have to build one from scratch to get it to do What I want it to?
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You do not say what language skills you have, as that will affect the choices you make. At a minimum you would need to be skilled at HTML, CSS and Javascript for the front-end. You then need a backend language and framwork, and good knowledge of database. Languages and frameworks to consider include:
- PHP
- Python with Flask or Django
- ASP.NET with C# or VB.NET
So you should consider which of the above you have any knowledge of and proceed from there. One of the best starting points for tutorials on the majority of the above is W3Schools Online Web Tutorials[^].
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I have some experience with React.js and C#.
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I am using C# in Visual Studio and am branching into web development. I was under the impression that C# can be used for front-end development but I don't see a way to do it. Do I need to use something else for the front end and c# for the back end?
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Are you looking for Blazor[^]?
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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I am not sure what I am looking for, I have experience with C#, and I want to use it for developing a website. I thought all I needed was C# but obviously, I was naive in my thinking. Would Blazer be the tool I am looking for?
Thanks for any help, as I am really new to website development.
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Blazor has the strapline "Use the power of .NET and C# to build full stack web apps without writing a line of JavaScript", so it's probably going to be close to what you're after. 
But if you're building a website, it won't hurt to have at least some knowledge of HTML[^], CSS[^], and JavaScript[^] (or preferably TypeScript[^]).
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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Thanks, I will look into that.
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