Backend - Lession 01 PHP foundation

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Lession 01 php base

1. php base

1. phpinfo (): output version number

   1. echo: Output text
   2. php.ini: php configuration file

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2. php variable

1. Naming variables must begin with $

2. Strictly case-sensitive

3. Special characters and can not start with a number (you can use an underscore)

4. unset: Destruction Variables

5. isset (): determines whether the variable exists isset(var1, var2)

6. Scope of simple variables : function 内部作用域and 外部作用域is not related

   <?php
      // 变量的作用域
      $test = 'hello';
   
      function test () {
          echo $test;     // 报错, 变量未定义
      }
   
      test();

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   2.1 Static variables:

   • static You can define static variables
   • Only initialized once, the previous value will be saved

   <?php 
   
       // 静态变量
       function total() {
          static $num = 2;
          $num *= 2;
          echo $num;
      }
   
      total();
      total();
      total();

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   2.2 superglobals:

   • $ GLOBALS: anywhere for PHP scripts to access the global variables
   • $ _SERVER: holds information about headers, paths, and script locations
   • $ _REQUEST: receiving data HTML form submission
   • $ _POST: receiving request data post
   • $ _GET: receiving a get request data
   • $ _FILES: receiving a data file
   • $ _ENV: is an array of server-side environment variables include
   • $ _COOKIE: COOKIE brought the acquisition request
   • $ _SESSION: acquisition request brought SESSION

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3. php difference between single and double quotes

1. Variable does not recognize single quotes, double quotes variable identification

2. Single quotes will not escape special characters, double quotation marks

   <?php 
   
       // 单双引号区别
       $name = '张三';
       $age = 18;
       $sex = 'man';
   
       echo "$name";   // 张三
       echo '$name';   // $name
   
       // 结论：单引号不解析变量，双引号解析变量
   
       echo "\n";      // 换行
       echo '\n';      // \n
   
       // 结论：单引号不会转义特殊字符, 双引号可以
   ?>

   1. And a string variable, with a point .stitching together

3. Double quotes may be spliced ​​together variables and strings "{$name}好好学习" -> "张三好好学习"

   1. Sets of double quotation marks single set of variables, output variables outside single quotes "'$name'" -> '张三'

4. Efficient than single quotes double quotes

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4. Data Type

1. 标量
    1.  整型：1   2  
    2.  浮点型：1.2    1.3
    3.  布尔类型：true    false
    4.  字符串：单双引号引起来的都是字符串
2. 混合类型（重点）
    1. 数组：array
    2. 对象：object
3. 特殊类型
    1. 空：null
    2. 资源：resource

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The data type conversion

1. Detection Data Type: gettype ()
2. Type Conversion
   1. intval (): is converted to an integer, integer
   2. floatval (): is converted to decimal, double
   3. strval (): converts a string, string
   4. boolval (): Converting to boolean, boolean
3. Analyzing the data type of commonly used functions
   1. is_array()
   2. is_string()
   3. is_bool()
   4. is_float()
   5. is_object()
   6. is_int()
   7. is_numeric (): number string will be converted to digital, and then determine, but not mixed non-numeric character
   8. is_resource (): determine whether the resource
   9. is_null()
   10. is_scalar (): determining whether a scalar

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6. Constant

1. Define constants:define('abc', 'abc');

2. Constant attention to points:

   * 常量可以直接用大写字母和下划线定义，不必加`$`符号

   • Assigned only scalar

   • Assigned only scalar
     * string constants can not be written
     

3. Determining whether the constant is defined:defined('常量名')

   1. System constants:

   2. __FILE__: Find your files

   3. __LINE__: Get the code where the number of lines

   4. __DIR__: Find files in the current directory

   5. PHP_OS: Get system information

   6. PHP_VERSION: Get Version Information

   7. __FUNCTION: Get the current function name

   8. M_PI:PI

   9. To understanding:

      • __MHTHOD__: Get the current members of the method name

      • __NAMESPACE__: Get the name of the current namespace
      • __TRAIT__: Get the current TRAIT name (multiple inheritance)

      • __CLASS__: Gets the current class name

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7. Operators

And other similar language

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8. several cases of false (conditional)

1. Strings and numbers:
   • '' 、 0 、'0'、 0.000
   • String '0.000'is true
2. Array: [](with different js)

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9. Process Analyzing

Basically the same as with other languages

expand:

1. Random Number: mt_rand (1, 10);

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10. cycle

As with other languages, variables within the loop is not local variables

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11.1 Functions

definition:function name() {}

1. function into the function library and custom functions

2. Custom library no longer function

3. Line Default parameters may be provided , with similar es6

4. When the default parameters not set, the argument being given less

The function is not case-sensitive

<?php 

    function Name($name = '刘程', $sex = '男') {
        echo '我是：'.$name.' . 性别：'.$sex;
        return true;
    }
    
    $temp = name('liucheng');       // 我是：liucheng . 性别：男
    echo '<br />'.$temp;            // 返回值 true

1. Variables and scope to see the title 2 variables
2. Line arguments of type constraints (important)

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11.2 line arguments and return values ​​of the function

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11.2.1 Line Type parameter constraints

After the line type parameter constraints, the function will convert the incoming data into the corresponding data, if not convert an error.

<?php

// 约束函数行参的类型
function test(string $name, int $num) {
    echo gettype($name).'<br />';
    echo gettype($num).'<br />';
}

test('liucheng', 20);
test(520, 20);
// test(520, "a");     // 报错, 'a' 不是整数

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11.2.2 return value constraint type

变量括号后面加一个 `:string` , 约束其返回值为 string ，不是 string 就会报错

<?php

// 约束函数返回值
function test(string $name, int $num):string {
    
    return $name.$num;
}

print_r(test('liucheng', 20).'<br>');

print_r(test(520, 20).'<br>');
echo test(520, "a").'<br>';     

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11.2.3 function of the variable parameter

Do not set the line parameters, you can get the parameters passed

1. func_get_args() : Get the parameters passed to form an array.
2. func_get_arg(n) : Obtaining parameters corresponding to the target position.

<?php

// 可变参数
function test() {
    $temp = func_get_args();
    echo func_get_arg(1).'<br>';
    return $temp;
}

print_r(test('liucheng', 20));      // 输出：Array ( [0] => liucheng [1] => 20 )

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12. Common Functions

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12.1 Mathematical Functions

1. random number
   • rand
   • mt_rand : 4 times better performance than the rand
2. Decimal
   • floor: rounding down
   • ceil: roundup
   • round: rounding rounding
3. other
   • abs: absolute value
   • pi: pi
   • M_PI: constants, and pi () function returns the same value
   • pow: exponential expression
   • max: maximum
   • min: minimum value

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12.2 String built-in functions

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1. Case conversion
   • strtolower: uppercase lowercase turn
   • strtoupper: uppercase lowercase turn
   • lcfirst: the first letter lowercase
   • ucfirst: capitalize the first letter
   • ucwords: capitalize the first letter of each word
2. Blank processing
   • trim: remove the first space
   • ltrim: remove head space
   • rtrim / chop: remove trailing spaces
3. Find positioning
   • strstr / strchr: detecting the first occurrence of the string in another string to the end of the content (case sensitive)
   • strrchr: detecting the last occurrence of the string to another string at the end of the content
   • stristr: strstr ignore case version
   • strpos: Returns the position of the first occurrence of the string (case-sensitive)
   • stripos: strpos ignore case version
   • strrpos: Returns the last position of occurrence of the string (case sensitive)
   • strripos: strrpos ignore case version
   • sbustr: substring extraction
   • strpbrk: return (any character search) content at the end of the first time to the (case-sensitive)
4. Compare
   • strcmp: binary comparison string
   • strcasecmp: strcmp case-insensitive comparison
   • strnatcmp: the use of a " natural ordering " algorithm to compare two strings (case sensitive), in the natural algorithm, the digital number less than 2 10. Ordering computer, 2 is less than 10, because the first number is less than 2 10.
   • strnatcasecmp: strnatcmp: ignore case version

5. order

   • str_shuffle: sequential random string upset
   • strrev: string in reverse order

6. Change

   • chr: The ASCII value into character

   To be continued. . .

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12.3 array of built-in functions