Shulou(Shulou.com)06/03 Report--

This article introduces the relevant knowledge of "what is the necessity of array non-numeric key quotation marks". In the operation of actual cases, many people will encounter such a dilemma. Next, let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

I've seen a lot of people operate on arrays without using quotation marks for non-numeric key names in the array.

The copy code is as follows:

$array [key] = $value

I can understand that some people may think that such code is neat and can be executed properly.

What's more, if he's "lucky" with a good configuration of php:

The copy code is as follows:

Error_reporting = ~ E_NOTIC

He may always be immersed in his "neat" style, can't see any NOTICE hints, and won't realize how much performance he can lose if he does so.

Come on, let's take a look:

Good.php:

The copy code is as follows:

Bad.php:

The copy code is as follows:

Look at the elapsed time (multiple average time):

In quotation marks:

The copy code is as follows:

$time php-f good.php

Real 0m0.013s

User 0m0.005s

Sys 0m0.007

Without quotation marks:

The copy code is as follows:

$time php-f bad.php

PHP Notice: Use of undefined constant bad-assumed 'bad' in / home/huixinchen/tmp/bad.php

On line (line 999 NOTICE is omitted here)

Real 0m0.100s

User 0m0.020s

Sys 0m0.029

Look, how different is it?

Well, maybe we should simulate the situation of those "lucky" people, get rid of the expenses spent on recording NOTICE, and see ~

The copy code is as follows:

$time php-f bad.php

Real 0m0.037s

User 0m0.018s

Sys 0m0.018

We can see that, basically, the efficiency loss of using quotation marks and not using quotation marks is more than 3 times.

So where are these losses of efficiency?

Let's take a look at the OPCODE sequence generated by the two files:

Good.php:

The copy code is as follows:

Filename: / home/huixinchen/tmp/good.php

Compiled vars:! 0 = $array,! 1 = $I

Line # op fetch ext return operands

20 INIT_ARRAY ~ 0

1 ASSIGN! 0, ~ 0

3 2 ASSIGN! 1, 0

4 3 PRE_INC $3! 1

4 IS_SMALLER ~ 4 $3, 1000

5 JMPZ ~ 4,-> 9

5 6 ZEND_ASSIGN_DIM! 0, 'good'

7 ZEND_OP_DATA 2, $6

6 8 JMP-> 3

8 9 RETURN 1

10 * ZEND_HANDLE_EXCEPTIO

Bad.php:

The copy code is as follows:

Filename: / home/huixinchen/tmp/bad.php

Compiled vars:! 0 = $array,! 1 = $I

Line # op fetch ext return operands

20 INIT_ARRAY ~ 0

1 ASSIGN! 0, ~ 0

3 2 ASSIGN! 1, 0

4 3 PRE_INC $3! 1

4 IS_SMALLER ~ 4 $3, 1000

5 JMPZ ~ 4,-> 10

5 6 FETCH_CONSTANT ~ 5 'bad'

7 ZEND_ASSIGN_DIM! 0, ~ 5

8 ZEND_OP_DATA 2, $7

6 9 JMP-> 3

8 10 RETURN 1

11 * ZEND_HANDLE_EXCEPTIO

We can see (in fact, according to the hint of NOTICE) that PHP will get the key name without quotation marks as a constant, throw a NOTICE when it cannot be found, and then generate a string according to the "constant specification", and then use this string as the key name to continue.

If you are smart, you will surely think that the following unexpected mistakes may occur:

The copy code is as follows:

Define ('key_name',' laruence')

....

/ / many lines of code are omitted

$array [key _ name] = 2; / / becomes $array ['laruence'] = 2

/ / will you be very depressed about such a mistake?

Do you understand? The key names of non-numeric keys in the array must have quotation marks.

Oh, remember someone would say that when string variables are replaced, writing quotation marks will lead to errors

Well, the standard way of writing:

The copy code is as follows:

$string = "variable value is {$array ['key']}"

I quite agree with "be lazy", but lazy should also have principles.

Finally, good code should not be camouflaged by turning off error_reporting.

Note: the logic of constant cannot be found in FETCH_CONSTANT OPCODE:

The copy code is as follows:

....

If (! zend_get_constant (opline- > op2.u.constant.value.str.val)

Opline- > op2.u.constant.value.str.len, & EX_T (opline- > result.u.var) .tmp_var TSRMLS_CC) {

Zend_error (E_NOTICE, "Use of undefined constant% s-assumed'% s"

Opline- > op2.u.constant.value.str.val

Opline- > op2.u.constant.value.str.val)

EX_T (opline- > result.u.var). Tmp_var = opline- > op2.u.constant;// get the "constant" name string

Zval_copy_ctor (& EX_T (opline- > result.u.var) .tmp_var); / / allocate space to generate a string

}

....

This is the end of the content of "what is the necessity of array non-numeric key quotation marks". Thank you for your reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.