This article mainly introduces the OpCode principle of PHP, and analyzes the relevant compilation mechanism and operating principle of the PHP program in more detail. Friends in need can refer to it
OpCode is a kind of PHP script compiled Intermediate language, like Java's ByteCode, or .NET's MSL. This article is mainly based on "Understanding OPcode" and the Internet. It is specially recorded based on personal understanding and modification:
PHP code:
<?php echo "Hello World"; $a = 1 + 1; echo $a; ?>
PHP will go through the following 4 steps when executing this code:
1. Scanning (Lexing), convert PHP code into language fragments (Tokens)
2. Parsing, convert Tokens into simple And meaningful expression
3. Compilation, compiles the expression into Opocdes
4. Execution, executes Opcodes sequentially, one at a time, thereby realizing the function of PHP script.
Note: Some current caches, such as APC, can enable PHP to cache Opcodes. In this way, every time a request comes, there is no need to repeat the first three steps, which can greatly improve the execution speed of PHP. .
First, Zend/zend_language_scanner.c will perform lexical analysis on the input PHP code based on Zend/zend_language_scanner.l (Lex file), thereby obtaining "words" one by one, which PHP4.2 began to provide There is a function called token_get_all. This function can scan a piece of PHP code into Tokens;
will get the following results:
Array ( [0] => Array ( [0] => 367 [1] => <?php [2] => 1 ) [1] => Array ( [0] => 370 [1] => [2] => 2 ) [2] => Array ( [0] => 316 [1] => echo [2] => 2 ) [3] => Array ( [0] => 370 [1] => [2] => 2 ) [4] => Array ( [0] => 315 [1] => "Hello World" [2] => 2 ) [5] => ; [6] => Array ( [0] => 370 [1] => [2] => 2 ) [7] => Array ( [0] => 309 [1] => $a [2] => 3 ) [8] => Array ( [0] => 370 [1] => [2] => 3 ) [9] => = [10] => Array ( [0] => 370 [1] => [2] => 3 ) [11] => Array ( [0] => 305 [1] => 1 [2] => 3 ) [12] => Array ( [0] => 370 [1] => [2] => 3 ) [13] => + [14] => Array ( [0] => 370 [1] => [2] => 3 ) [15] => Array ( [0] => 305 [1] => 1 [2] => 3 ) [16] => ; [17] => Array ( [0] => 370 [1] => [2] => 3 ) [18] => Array ( [0] => 316 [1] => echo [2] => 4 ) [19] => Array ( [0] => 370 [1] => [2] => 4 ) [20] => Array ( [0] => 309 [1] => $a [2] => 4 ) [21] => ; [22] => Array ( [0] => 370 [1] => [2] => 4 ) [23] => Array ( [0] => 369 [1] => ?> [2] => 5 ) )
The returned result, strings, characters, and spaces in the source code will be returned unchanged. Characters in each source code will appear in the corresponding order. However, other items such as tags, operators, and statements will be converted into an Array containing two parts: Token ID (that is, the corresponding code for changing the Token inside Zend, such as T_ECHO, T_STRING), and the original code in the source code. Content.
The next step is the Parsing stage. Parsing will first discard the excess spaces in the Tokens Array, and then convert the remaining Tokens into simple expressions one by one
1. echo a constant string
2. add two numbers together
3. store the result of the prior expression to a variable
4. echo a variable
Then, change the Compilation stage, it Tokens will be compiled into op_arrays one by one. Each op_arrayd contains the following 5 parts:
1. The identification of the Opcode number indicates the operation type of each op_array, such as add, echo
2. Result Store the Opcode result
3. Operand 1 is the operand of Opcode
4. Operand 2
5. The extended value is an integer to distinguish the overloaded operator
For example , the PHP code will be Parsed into:
[root@localhost html]# /usr/local/php/bin/php -dvld.active=1 hello.php Branch analysis from position: 0 Return found filename: /var/www/html/hello.php function name: (null) number of ops: 6 compiled vars: !0 = $a line # op fetch ext return operands ------------------------------------------------------------------------------- 2 0 ECHO 'Hello+world' 3 1 ADD ~0 1, 1 2 ASSIGN !0, ~0 4 3 ECHO !0 6 4 RETURN 1 5* ZEND_HANDLE_EXCEPTION Hello world2
Each operand is composed of the following two parts:
a) op_type: IS_CONST, IS_TMP_VAR, IS_VAR, IS_UNUSED, or IS_CV
b) u, a union, which stores the value (const) or lvalue (var) of the operand in different types according to the op_type. )
As for var, each var is different. IS_TMP_VAR, as the name suggests, this is a temporary variable that saves some results of op_array for use in the next op_array. The u of this type of operand stores a handle (integer) pointing to the variable table. This type of operand is generally used~ The beginning, such as ~0, represents the unknown temporary variable IS_VAR at No. 0 in the variable table. This is our general variable. They begin with $ to represent IS_CV, which represents the type used by compilers after ZE2.1/PHP5.1. cache mechanism, this variable stores the address of the variable referenced by it. When a variable is referenced for the first time, it will be CVd. Subsequent references to this variable do not need to look up the active symbol table again. CV variables are represented by starting with !.
$a variable is optimized to !0.
Summary: The above is the entire content of this article, I hope it will be helpful to everyone's study.
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The above is the detailed content of Detailed explanation of OpCode principle in PHP. For more information, please follow other related articles on the PHP Chinese website!

php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($number))”;2、利用“~”位运算符将负数取反加一,语法“~$number + 1”。

实现方法:1、使用“sleep(延迟秒数)”语句,可延迟执行函数若干秒;2、使用“time_nanosleep(延迟秒数,延迟纳秒数)”语句,可延迟执行函数若干秒和纳秒;3、使用“time_sleep_until(time()+7)”语句。

php除以100保留两位小数的方法:1、利用“/”运算符进行除法运算,语法“数值 / 100”;2、使用“number_format(除法结果, 2)”或“sprintf("%.2f",除法结果)”语句进行四舍五入的处理值,并保留两位小数。

判断方法:1、使用“strtotime("年-月-日")”语句将给定的年月日转换为时间戳格式;2、用“date("z",时间戳)+1”语句计算指定时间戳是一年的第几天。date()返回的天数是从0开始计算的,因此真实天数需要在此基础上加1。

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\ \;||\xc2\xa0)/","其他字符",$str)”语句。

php判断有没有小数点的方法:1、使用“strpos(数字字符串,'.')”语法,如果返回小数点在字符串中第一次出现的位置,则有小数点;2、使用“strrpos(数字字符串,'.')”语句,如果返回小数点在字符串中最后一次出现的位置,则有。

在PHP中,可以利用implode()函数的第一个参数来设置没有分隔符,该函数的第一个参数用于规定数组元素之间放置的内容,默认是空字符串,也可将第一个参数设置为空,语法为“implode(数组)”或者“implode("",数组)”。

在php中,可以使用substr()函数来读取字符串后几个字符,只需要将该函数的第二个参数设置为负值,第三个参数省略即可;语法为“substr(字符串,-n)”,表示读取从字符串结尾处向前数第n个字符开始,直到字符串结尾的全部字符。


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