What are the commonly used system functions for files in PHP? What is the principle of loading files?

The previous article introduced to you "How to get the specifications of PHP framework development in one minute? 》, this article continues to introduce to you what are the commonly used system functions for files in PHP? What is the principle of loading files? It has certain reference value. Friends in need can refer to it. I hope it will be helpful to everyone.

The file contains commonly used system functions:

(1) Output-related functions;

print(); similar to the content provided by echo output, which is essentially a structure (not a function), returns 1, and does not need to use parentheses;

print_r(); similar to var_dump, but simpler than var_dump, it will not output the data type, but only the value (which is more commonly used for array printing)

Let’s take the code as an example;

<?php
//系统函数
//输出相关
echo print(&#39;hello world<br/>&#39;);
print &#39;hello world<br/>&#39; ;
$a = &#39;hello world<br/>&#39;;
print_r($a);

For direct output print The reason why function wrapping is not used is because it is just a structure and not a real function. For print_r() like this, it usually operates on variables, such as the code we wrote above; we can see the second result in the code There is a 1 in front, which is the value output by echo;

The code demonstration results are as follows:

(2) Functions related to time

• date() corresponds to the time period in the specified format. If there is no specified timestamp, then the current timestamp will be interpreted by default,

• time(): Get the timestamp corresponding to the current time

• microtime(): Get the time at the microsecond level

us Take the code as an example;

<?php
//系统函数
//输出相关
echo print(&#39;hello world<br/>&#39;);
print &#39;hello world<br/>&#39; ;
$a = &#39;hello world<br/>&#39;;
print_r($a);
echo '
';
//时间函数
echo date('Y 年 m 月 d 日 H:i:s' ,12345678),'
;
echo time(),'
';
echo microtime(),'
';

(3) Functions related to numbers

• max()

• main()

• rand()

• mt_rand()

• ##round()

Execution process of PHP code:

1. Read the code file (PHP program).

2. Compile: Convert PHP code into bytecode (generate opcode).

3. zendengine parses the opcode and performs logical operations according to the bytecode

If a syntax error occurs during the compilation of the PHP file, it will fail (will not be executed) ); But if there is an error in the included file, the system will not report an error until the include statement is executed.

4. Convert to the corresponding HTML code

File loading principle:

1: Load the file (include or require), the system will automatically include the code in the file, which is equivalent to embedding it into the current file;

2: Loading location: Where to load, the location where the code in the corresponding file is embedded is Corresponding include location;

3: Files included in PHP are compiled separately;

Recommended study: "

PHP Video Tutorial"

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