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PHP quotation-what are the attention problems of symbols? I believe many inexperienced people are at a loss about this. Therefore, this paper summarizes the causes and solutions of the problem. Through this article, I hope you can solve this problem.

PHP quotation-symbol is a difficult knowledge point to master. Novices should pay more attention to this when actually writing code, because if you misunderstand the use of PHP references & symbols, it will lead to errors in the whole code you write.

Many people misunderstand that references in php are the same as pointers in C. in fact, this is not the case, and it is very different. Pointers in C language need to be defined using * except that they do not need to be explicitly declared in the process of array passing. The function of pointing to addresses (similar pointers) in php is not implemented by the user, but by the Zend core. PHP references & symbols adopt the principle of "copy on write", that is, variables or objects pointing to the same address will not be copied unless a write operation occurs. For example, the following code:

$a = array ('axiomatic clockwise.. roomn'); $b = $a

If the program only executes here, $b and $b are the same, but not like C, $an and $b occupy different memory space, but point to the same piece of memory, this is the difference between php and c, and does not need to be written as $baked memory to represent the memory of $b pointing to $a, zend has already implemented the reference for you, and zend will be very smart to help you determine when to deal with it this way and when not to do so.

If you continue to write the following code later, add a function, pass parameters through the PHP reference & symbol, and print out the array size.

Function printArray (& $arr) / / reference passing {print (count ($arr));} printArray ($a)

In the above code, we pass the $an array into the printArray () function through the PHP reference & symbol, and the zend engine thinks that printArray () may cause a change to $a, and then automatically produces a copy of $a data for $b and re-requests a piece of memory for storage. This is the "copy-on-write" concept mentioned earlier.

If we change the above code to look like this:

Function printArray ($arr) / / value passing {print (count ($arr));} printArray ($a)

The above code passes the $a value directly into printArray (), and there is no reference passing, so there is no write-time copy.

You can test the execution efficiency of the above two lines of code, such as adding a loop 1000 times to see how long it takes to run. The result will let you know that incorrect use of PHP references & symbols can lead to performance degradation of more than 30%.

After reading the above, have you mastered the ways to pay attention to PHP quotes & symbols? If you want to learn more skills or want to know more about it, you are welcome to follow the industry information channel, thank you for reading!

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