Php Study Notes (1)

1. the execution operator is a backslash (''), which is equivalent to the shell_exec () function. Run the $ out 'dir' command to list the current directory and file information. define the constant define (str, thisisaconstvariableBR); echostr; 3. the string is enclosed in single or double quotation marks. The difference is that when a variable appears in double quotes, it is replaced with a variable.

1. the execution operator is a backslash (''), which is equivalent to the shell_exec () function. Run the $ out = 'dir' command to list the current directory and file information. define the constant define (str, this is a const variableBR); echo str; 3. the string is enclosed in single or double quotation marks. The difference is that when a variable appears in double quotes, it is replaced with a variable.

1. The execution operator is a backslash (''), which is equivalent to the shell_exec () function and runs a system command.

$ Out = 'dir'; // list the current directory and file information

2. Define Constants

define("str","this is a const variable
");echo str;

3. String

Enclosed in single or double quotation marks. The difference is that when a variable appears in double quotes, it is replaced with the variable value.

$ A = 10; echo ("variable is $ a"); echo ('variable is $ A'); // The result is: variable is 10 variable is $

4. Accept data

Use the variable $ _ POST to read form data. If the control's name attribute is c1, use the following method to obtain its value:

$ _ POST ['c1']

Index. php file

ShowInfo. php file

If (isset ($ _ POST ['submit ']) & $ _ POST ['submit']) {echo ("
Username: ". $ _ POST ['username']."
");}

5. Accept the parameter information in the URL

PASS Parameters in the URL in the format:

Http: // URL/Webpage file? <参数1> = & <参数2> =

Accept parameter: use variable:$ _ GET ['parameter name']

SubmitShowInfo. php file echo ("name:". $ _ GET ['name']."
"); Echo (" sex: ". $ _ GET ['sex ']);

6. Define an array

Array ([key =>] value

,...

)

The keyword can be an integer or a string. If the keyword is omitted, the next digit is used as the keyword, starting from 0.

$ Arr = array ("first" => "Cpu", "disk", 2 => "memory", "screen"); print_r ($ arr); // result: array ([first] => Cpu [0] => disk [2] => memory [3] => screen)

Multi-dimensional array

$ Arr [0] [0] = "CPU"; $ arr [2] [3] = "memory"; print_r ($ arr); // result: array ([0] => Array ([0] => CPU) [2] => Array ([3] => memory ))

7. array Functions

Print_r ($ arr );// Output Array

$ Tmp = array_change_key_case ($ arr, CASE_LOWER); // OR CASE_UPPER

Returns an array of all string keywords in lowercase or upper case.

$ Tmp = array_count_values ($ arr );

Count the number of times all values appear in the array and return the result to another array.

Array_fill:Fill the array with the specified value

Array_fill (int start_index, int num, value );

$ Arr = array_fill (2, 2, "element"); print_r ($ arr); Result: Array ([2] => element [3] => element)

Bool array_key_exists (key, $ arr );// Check whether the specified keyword in the array exists

$ Tmp = array_keys ($ arr [, value]);// Returns an array listing all keywords. If value is specified, only the keyword of value is returned.

$ Tmp = array_merge ($ arr1, $ arr2 ,...);// Combine multiple numbers. If the keywords are the same, the previous one will be overwritten.

Array_pop ($ arr );// Bring up the last element of the array

Array_push ($ arr, value1, value2 ,...);// Press multiple elements to the end of the array, and numbers are used as keywords.

Array_reverse ($ arr );// Reverse array Arrangement

$ Tmp = array_sum ($ arr );// Sum of Elements

Array_unique ($ arr );// Delete repeated elements in the array

Arsort ($ arr );// Sort in descending order

Asort ($ arr );// Sort in ascending order

8. traverse the Array

$ Arr = array ('A' => 'A', 'B' => 'B', 'C' => 'C', "CPU", "memory ", '4'); foreach ($ arr as $ val) {echo $ val. "";} // OR: for ($ I = 0; $ I
 
  

  

  
The results of the two methods are as follows: a B c CPU memory 4
  
Sizeof ($ arr)Get the number of array elements,Next ($ arr)The function moves the pointer to the next position,Current ($ arr)Obtains the elements under the current pointer.
  
9. Variable Length Parameter List
  
When defining a function, no parameter is specified. In the function body, obtain parameter information through the following three functions:
  
Func_num_args ():Number of returned Parameters
  
Func_get_arg ($ I):Returns the parameter with subscript I.
  
Func_get_args ():Returned parameter Array
  
 
  
Function sum () {$ num = func_num_args (); $ sum = 0; for ($ I = 0; $ I <$ num; $ I ++) $ sum = $ sum + func_get_arg ($ I); echo "the sum is $ sum
";}Or: function sum () {$ num = func_num_args (); $ sum = 0; $ arg_list = func_get_args (); for ($ I = 0; $ I <$ num; $ I ++) $ sum = $ sum + $ arg_list [$ I]; echo "the sum is $ sum
";}