PHP Programming Basic Grammar Quick start manual _php tips

After the PHP script is named. PHP, the code is placed in the parentheses below:

<?php ...
? >

Echo can print information, similar to printf.

<?php
echo "Hallo world";
? >

End Each statement with a semicolon;.

PHP supports three kinds of annotation methods:

<?php
//First

# Second/

*
This is
multiline comment/
?>

In PHP, the capitalization of functions, classes, and keywords is the same thing:

<! DOCTYPE html>
 
 

However, all variables are case sensitive and need to be case-sensitive.

<?php
$color = "Red";
$Color = "BLACK";
echo "My car is". $color. "<br>";
echo "My car is". $Color. "<br>";
? >

The above example also points to the definition of variables and the syntax of string concatenation.

Variable naming rules:

PHP Variable rules:

• The variable begins with the $ symbol followed by the name of the variable
• Variable names must begin with a letter or underscore
• Variable names cannot begin with a number
• Variable names can only contain alphanumeric characters and underscores (A-Z, 0-9, and _)
• Variable names are case sensitive ($y and $Y are two different variables)
• The variable is created the first time the value is assigned. You do not need to declare the type of the variable.

Variables can have three different scopes:

PHP has three different scope of variables:

1. Local (partial)
2. Global (overall)
3. Static (quiescent)

A variable declared outside of a function owns the Global scope and can only be accessed outside of the function.
Variables declared within a function have a local scope and can only be accessed within a function.
The following example tests variables with local and global scope:

<?php
$x = 5;//global scope function

myTest () {
 $y = 10;//local scope
 echo "<p> test function internal variable:</p>";
 echo "Variable x is: $x";
 echo "<br>";
 echo "Variable y is: $y";
} 

MyTest ();

echo "<p> variable:</p> outside of test function";
echo "Variable x is: $x";
echo "<br>";
echo "Variable y is: $y";
? >

Run Result:

To test variables inside a function:

The variable x is:
Variable y is: 10
To test a variable other than a function:

The variable x is: 5
The variable y is:
The odd thing is why global variables cannot be accessed within local functions.

You can actually access it, but you need help with the Global keyword:

The global keyword is used to access globally variables within a function.
To do this, use the Global keyword before the variable (inside the function):

<?php
$x =5;
$y =10;

function MyTest () {
 global $x, $y;
 $y = $x + $y;
}

MyTest ();
Echo $y; Output
?>

PHP stores all of the global variables in an array named $GLOBALS [index] at the same time. The subscript contains the variable name. This array is also accessible within the function and can be used to directly update global variables.

<?php
$x =5;
$y =10;

function MyTest () {
 $GLOBALS [' y ']= $GLOBALS [' x ']+ $GLOBALS [' y '];
} 

MyTest ();
Echo $y; Output
?>

Typically, all variables are deleted when the function completes execution. However, sometimes I need not delete a local variable. This needs to be static:

<?php

function MyTest () {
 static $x =0;
 echo $x;
 $x + +;
}

MyTest ();
MyTest ();
MyTest ();

? >

Both Echo and print are available in PHP, and the only difference is that the print return 1,echo has no return value.

The Strlen function can return the length of a string.

The Strpos function is used to determine the position of another string:

<?php
Echo strpos ("Hello world!", "World");
? >

Use the Define function to define constants:

<?php
define ("greeting", "Welcome to w3school.com.cn!");
echo greeting;
? >

The Define function also has a third parameter that specifies whether it is case sensitive.

PHP's if-else statements are very similar to other languages, for example:

<?php
$t =date ("H");

if ($t < "") {
 echo "Have a good morning!";
} elseif ($t < "") {
 echo "Have a good day!";
} else {
 echo "Have a good night!";
}
? >

Switch-case statement:

<?php
switch ($x)
{case
1:
 echo "Number 1";
 break;
Case 2:
 echo "Number 2";
 break;
Case 3:
 echo "Number 3";
 break;
Default:
 echo "No number between 1 and 3";
>

While, the for statement and other languages are no different, look at foreach:

<?php 
$colors = Array ("Red", "green", "blue", "yellow"); 

foreach ($colors as $value) {
 echo "$value <br>";
}
? >

The real power of PHP comes from its function, which has 1000 built-in functions.

User-defined function declarations begin with a "function" of the form:

function functionname () {
The executed code;
}
As an example:

<?php
function writemsg () {
 echo "Hello world!";
}

Writemsg (); Call function
?>

//contains parameters
<?php function
familyname ($fname, $year) {
 echo $fname Zhang. Born in $year <br> ";
}

Familyname ("Li", "1975");
Familyname ("Mr", "1978");
Familyname ("Tao", "1983");
? >

//default parameter
<?php
function setheight ($minheight =50) {
 echo "the" is: $minheight <br > ";
}

SetHeight ();
SetHeight (); The default value of
setheight (135) will be used.
SetHeight (a);
? >

//return value
<?php
function sum ($x, $y) {
 $z = $x + $y;
 return $z;
}

echo "5 + 10 =". SUM (5,10). "<br>";
echo "7 + 13 =". SUM (7,13). "<br>";
echo "2 + 4 =". SUM (2,4);
? >

In PHP, there are three types of arrays:

1. Index array-an array with a numeric index
2. Associative array-An array with the specified key
3. Multidimensional array-An array that contains one or more arrays

Indexed arrays:

$cars =array ("Volvo", "BMW", "SAAB");
<?php
$cars =array ("Volvo", "BMW", "SAAB");
echo "I like". $cars [0]. ", " . $cars [1]. "and". $cars [2]. ".";
? >

//Count
<?php
$cars =array ("Volvo", "BMW", "SAAB");
echo count ($cars);
? >

//Variable index array
<?php
$cars =array ("Volvo", "BMW", "SAAB");
$arrlength =count ($cars);

For ($x =0 $x < $arrlength; $x + +) {
 echo $cars [$x];
 echo "<br>";
>

Associative arrays:

$age =array ("Peter" => "," "Ben" => "Panax Notoginseng", "Joe" => "43");

Or

$age [' Peter ']= '];
$age [' Ben ']= ' for "Panax Notoginseng";
$age [' Joe ']=];

<?php
$age =array ("Bill" => "," "Steve" => "Notoginseng", "Peter" => "the");
echo "Peter is". $age [' Peter ']. "Years old."
>




//Traverse
<?php
$age =array ("Bill" => "," "Steve" => "Notoginseng", "Peter" => "the");

foreach ($age as $x => $x _value) {
 echo "key=". $x. ", value=." $x _value;
 echo "<br>";
>

Array sorting methods have the following:

• Sort ()-sort the array in ascending order
• Rsort ()-Sort in descending pairs
• Asort ()-Sort the associative array in ascending order by value
• Ksort ()-Sort the associative array in ascending order according to the key
• Arsort ()-Sort the associative array in descending order by value
• Krsort ()-Sort the associative array in descending order according to the key

It is more difficult to understand the sort of key-value pairs.

<?php
$age =array ("Bill" => "," "Steve" => "Notoginseng", "Peter" => "the");
Asort ($age);
? >

<?php
$age =array ("Bill" => "," "Steve" => "Notoginseng", "Peter" => "the");
Ksort ($age);
? >

Super global variables, which are predefined global variables, can be used everywhere, with special meaning:

• $GLOBALS: Referencing all variables available in the global scope
• $_server: Holds information about headers, paths, and script locations.
• $_request: Used to collect data submitted by HTML forms.
• $_post: Used to collect form data after submitting an HTML form that submits method= "post". is also commonly used to pass variables.
• $_get:$_get can also be used to collect form data after submitting an HTML form (method= "get").
• $_files
• $_env
• $_cookie
• $_session

Other content can be found in form processing.