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For more information about PHP and syntax, see php.net’s documentation :PHP Manual or PHP Tutorial

PHP knowledge

PHP (PHP: Hypertext Preprocessor) is a common open source scripting language.

PHP file

PHP files can contain text, HTML, JavaScript code, and PHP code
The PHP code executes on the server and the result is returned to the browser in pure HTML
The default file extension for PHP files is “.php”

PHP knowledge

Start tag<? phpAnd closing tag? >. The content between the opening and closing tags is parsed and executed as PHP code.
Get the get request parameters$_GET

<body>
  <div id="head"></div>
  <div id="content">
    
      
      $id=$_GET['id'];// Get the get query string argument
      if($id= ='1') {// Read the contents of 1. TXT and print echo
        $str = file_get_contents('./1.txt');
        echo $str;
      }      
    ? >
  </div>
  <div id="footer"></div>
</body>
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echooutput

Echo – can print one or more strings print – can print only one string and always return 1


      
echo "I want to learn PHP! 

";
echo "This is one."."String,"."Used"."More than"."Parameters.";

print "I want to learn PHP!";
? >
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use//and/ * * /annotate
Variable to$At the beginning, there is no command to declare a variable, the variable is created at the first assignment, can be used directly, alphanumeric underscore (cannot be the first digit), the first definition of the variable should be given a value.
Constants cannot be changed. Define constantsDefine (' PI ', 3.1415926)A constant consists of letters, underscores (_), and numbers. The number cannot start with a letter$Modifier).Constants are available throughout the script. Constants can only be Boolean, INTEGER, float, string.
Define (' PI ', 3.1415926)Is a function that returns true if a constant is defined and false if it is not.
var_dump()Used to output information about variables.print_r()Used to print variables and present them in a form that is easier to understand.
PHP data types:

Scalar types — String (String), Integer (Integer, PHP_INT_MAX and PHP_INT_MIN), Float (Float is a number with a decimal part, or an exponent), Boolean (Boolean);

Scalar values cannot be split into smaller units.

Compound types — Array, Object, callable;

Special type — resource, NULL (NULL, case insensitive).

An array of. usearray()or[](>=php5.4) Define an array

The count() function returns the length of the array

Indexed array: An array with a numeric index.
Associative array: An array with a specified key. An array that uses the specified key assigned to the array (the key is either string or int)
Multidimensional array – An array containing one or more arrays


       
   // Create an indexed array
   $cars=array("Volvo"."BMW"."Toyota"); 
   // $cars=["Volvo","BMW","Toyota"];
   // $cars[0]="Volvo";
   // $cars[1]="BMW";
   // $cars[2]="Toyota";
   var_dump($cars);
 
   echo count($cars); // count() the length of the array

  // Iterate over the indexed array
   $arrlength=count($cars);
   for($i=0;$i<$arrlength;$i{+ +)echo $cars[$i];
     echo "<br>";
   }

   echo "<br>";

   $arrlength=count($cars);
   
    // Array element types are inconsistent
    $stu0 = array('Joe'.13);

   An associative array is an array that uses the specified key (string or int) assigned to it.
   // There are two ways to create associative arrays
   $stu1 = array(
     'name'= >'Joe'.'age'= >13
   );
   $stu2['name'] ='bill';
   $stu2['age'] =14;

   / / traverse
   foreach($stu2 as $key= >$value)
   {
       echo $key . " 是：" . $value;
       echo "<br>";
   }

? >
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Which values are equal to FALSE

1. The Boolean value FALSE itself
1. The integer 0
1. Floating point 0.0
1. Empty string and string “0”
1. An array that does not contain any elements
1. Special type NULL(including variables that have not yet been assigned)
1. Generate SimpleXML objects from empty tags

All other values are considered TRUE(including any resource and NAN)

(bool) Type conversion


      
  $int_a=0;
  var_dump( (bool)$int_a ); // false
? >
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Expression: Anything that has a value.

Expressions are one of the most important cornerstones of PHP; almost anything you write is an expression.

The most basic expressions are constants and variables. If $a = 5, the value of “5” is 5, and “5” is an expression with the value of “5”; $b = $a, $a is an expression that also has a value of 5.

Functions are also expressions.

PHP is an expression oriented language

The operator

Arithmetic operator

The assignment operator

Increment decrement operator

Comparison operator

Logical operator

String operator

Process control

Sequential standard execution is sequential execution
conditions

1) – if statements

A direct use of if(… elseif… Else) statement condition judgment and execution.

Another way to use
and
implement conditional statements (
,
,
and
)


      
    if(true) {echo ' This is a heading 
';
        echo ' This is a heading 
';
    }
    else if(true){

    }
    elseif(true){

    }
    else{}? >


       if(true) :? >
    <h1  class="head"> < span style = "max-width: 100%h1>
<?php endif; ? >Copy the code

2) – a switch statement

Use the Switch statement to avoid lengthy if.. elseif.. Else code block.

switch (expression)
{
case label1:
  // expression = code executed at label1;
  break;  
case label2:
  // expression = code executed when label2;
  break;
default:
  // The code executed when the value of the expression satisfies all of the above cases;
}
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cycle

1) – while loop

while(true){

}
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Alternative syntax


       while() :? >
 // code

       endwhile; ? >
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2) – the foreach loop

foreach( $as as $a ){

}
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and

foreach( $as as $a_key= >$a_value ){

}
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Alternative syntax


       foreach(expr): ? >
 / / the loop body

       endforeach; ? >`
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3) – a for loop

You can specify the number of cycles.

for (init counter; test counter; increment counter) {
  code to be executed;
}

for ($x=0; $x< =10; $x{+ +)echo "The numbers are:$x <br>";
} 
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function


      
  function functionName($a.$b){}// Default value parameter
  function functionName($a.$b=4){

    / / the return value
    // return $value
  }
? >
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PHP variable scope: The scope of a variable is the part of the script where the variable can be referenced/used (scope).

PHP has four different variable scopes: local, global, static, and parameter

Local and global scopes

Variables defined outside all functions have global scope. Global variables can be accessed by any part of the script except functions. To access a global variable within a function, use the global keyword.

PHP stores all global variables in an array named $GLOBALS[name], which is internally accessible through $GLOBALS


      
$x=5;
$y=10;
 
function myTest()
{
    global $x.$y;
    $y=$x+$y;
}
 
myTest();
echo $y; / / output 15
? >
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Corresponds to the $GLOBALS mode


      
$x=5;
$y=10;
 
function myTest()
{
    $GLOBALS['y'] =$GLOBALS['x'] +$GLOBALS['y'];
} 
 
myTest();
echo $y;
? >
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The Static scope

When a function completes, all its variables are usually removed. However, if you want a local variable not to be deleted. You can use the static keyword when declaring a variable for the first time:

 
      
 function myTest()
 {
     static $x=0;
     echo $x;
     $x+ +;echo PHP_EOL;    / / a newline character
 }
  
 myTest();  / / 0
 myTest();  / / 1
 myTest();  / / 2
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Parameter Parameter scope (parameter)

Parameter declarations are part of function declarations.

function myTest($x)
{
    echo $x;
}

myTest('Galois');
myTest(8888);
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Classes and objects

Property declarations begin with the keyword public, protected, or private and are followed by a normal variable declaration.

Use of the var keyword

Class attributes must have qualifiers. In PHP, class attributes must be defined as either public, protected, or private. So if you don’t have those three modifiers, you have to use var. Var is treated as public since PHP5. Var is an alias for public.


      
  / / inheritance
  class ClassName extends ParentClass{
      /* Member variable */
      var $url;
      var $title;

    // constructor
    function __construct( $par1.$par2 ) {
       $this->url = $par1;
       $this->title = $par2;
    }

    // destructor
    function __destruct() {
       print "Destroyed" . $this->name . "\n";
   }

    function printIP()
    {
        echo $this->url;
        echo $this->title; }}// Create an object
  $obj=new ClassName();
? >
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File splitting

Modular programming. Use the require or include keyword to import other PHP files, and then use PHP code, functions, variables, and so on from that file

Require_once and include_once can introduce the same file multiple times without reporting an error. Both are introduced only once, and will not be introduced repeatedly.

Amy polumbo HP / / file

      
    function add($a.$b){
      return $a+$b;
    }
? >

P. HP / / file

      
require './a.php';  // The error level is higher than include
// include './a.php'; // The code can still be executed after the error is introduced

// require_once('./a.php'); // require_once "./a.php";
// include_once "./a.php"; // include_once('./a.php');

$c=add(3.4);
echo $c;
? >
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Commonly used functions

printf()Prints a formatted string
sprintf()Returns a formatted string
print()Outputs (a) string with only one argument.


      
  $name="Zhang";
  $age=16;

  // Format string output
  printf('I'm % S and I'm % D.'.$name.$age);  // Returns the length of the resulting string

  // Returns a formatted string
  $str=sprintf('I'm % S and I'm % D.'.$name.$age);
  echo $str;

  print('Print out');
  // Exit the current execution
  exit(a);? >
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print_r()Print variables in a nice format

Bool print_r (mixed $expression [, bool $return]) parameter Description

$expression: The variable to print. If a string, INTEGER, or float variable is given, the value itself will be printed. If an array is given, the keys and elements will be displayed in a certain format. Object is similar to an array.

$return: Optional, if true, the result is not printed but assigned to a variable, false, the result is printed directly.

PHP single quotes and double signals

The contents of single quotes are not interpreted (\n is not printed as a newline, variables are not parsed as variable values, etc.), i.e. the contents are the same as the input

The contents of the double quotes will be interpreted, that is, variables in the content will be parsed.

1. Insert single quotation marks between double quotation marks. If there are variables in single quotation marks, the variables will be interpreted
1. Because double quotes are interpreted, they are less efficient than single quotes, so use single quotes in YOUR PHP code. Double quotation marks are used when parsing contained variables

<pre></pre>Tag, used to leave content such as line feeds as is

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PHP basics and syntax points

PHP knowledge

PHP file

PHP knowledge

This is a heading

This is a heading

PHP basics and syntax points

PHP knowledge

PHP file

PHP knowledge

This is a heading

This is a heading

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