Summary of new features in php7

This article brings you a summary of the new features in php7. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

It has been almost three years since PHP7 was released, and it has now developed to version PHP7.2.9. Its release has brought great performance improvements to PHP, which is mainly due to PHP's deep optimization of the Zend engine and also reduces PHP's resource usage on the system.

The main changes are as follows:

• Abstract syntax tree

In previous versions of PHP, PHP code The ZendVM instruction is directly generated during the syntax parsing stage, that is, the opline instruction is directly generated in zend_language_parser.y, which couples the compiler and the executor. .

An abstract syntax tree is added to PHP7. First, the PHP code is parsed to generate an abstract syntax tree, and then the abstract syntax tree is compiled into ZendVM instructions. The addition of the abstract syntax tree makes the PHP compiler and executor well isolated. The compiler does not need to care about the generation rules of instructions. Then the executor compiles the abstract syntax tree into corresponding instructions according to its own rules. The executor also does not You need to care about what the syntax rules of this instruction look like.

• Native TLS

Native TLS (thread local storage) is used in PHP7 to save the thread's resource pool, simple To put it simply, __thread is used to identify a global variable, so that this global variable is exclusive to the thread, and modifications by different threads will not affect each other.

• Specify function parameters and return value types

In PHP7, you can specify the types of function parameters and return values.

• Changes in zval structure

PHP7 transfers the reference count to a specific value, which is more reasonable. In addition, the size of the zval structure has also been reduced from 24byte to 16byte. This is an optimization point where PHP7 can reduce system resource usage.

• Exception handling

Many operations in PHP5.x will directly throw error errors. In PHP7, most errors are changed to exception throws. In this way, it can be captured through try catch.

• Changes in HashTable

There are very big changes in HashTable in PHP7, the HashTable structure The size is reduced from 72byte to 56byte. At the same time, the array element Bucket structure is also reduced from 72byte to 32byte.

• Executor

no longer adopts the method of passing parameters in PHP7, but execute_data, opline Storage is performed through registers, which avoids frequent stack operations caused by passing parameters. At the same time, registers are accessed faster than memory.

• New parameter parsing method

PHP5.x parses function parameters through zend_parse_parameters(), PHP7 provides Another method retains the original method, but the new parsing method is faster.

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