PHP function comments

Author of PHP function comments : Axglephp function usage instructions, application examples, simplified comments , I hope it will help you learn PHP. 1. Print_r  () Print the easy-to-understand information about variables. If it is an array, the structure information of the array is displayed. . For example: <PRE> <? PHP  $ = Array ('A' => 'apple', 'B' => 'bana', 'c' => Array ('X', 'y', 'Z' ));  Print_r ($  ); ?> </PRE> Axgle comments : View the structure information of any array, yesProgramA required tool for debugging. If any returned result is an array "function", you only need print_r to check the details at a glance! 2. Var_export  () Outputs or returns a variable string, indicating that the function returns structure information about the variable passed to the function, which is similar to print_r, the difference is that the returned representation is valid in PHP.Code. You can set the second parameter of the function  True  To return the expression of the variable. For example : <PRE> <? PHP  $ = Array (1, 2,Array ("A", "B", "C" ));  Var_export ( $  );  Echo "<HR>" ;  $ V = Var_export ( $ , True  );  Echo   $ V  ; ?> </PRE>Axgle comments : In the above example, $ V = Var_export ( $ , True ) PHP code is returned ~~ You can save it as a PHP file. What is saved as a PHP file? This can be used as a "cache". You can include it directly when necessary. 3. File  ()  File () Returns the object as an array. Each element in the array is a corresponding line in the file, including line breaks. If it fails File () Return False  . <PRE> <?PHP  //  Reads a file into an array.  $ Lines = File ('Test.txt' );  //  View the structure of this array  Print_r ( $ Lines  ); ?> </PRE> Axgle comments : File () Functions are a function that surprised me when I first came into contact with PHP. Compared with the previousC LanguageI felt that there was no more convenient file read/write method than the file () function. 4. Phpinfo  () Print PHP-related information, such as the PHP version, Function Support, and global variables. . For example : <? PHP  Phpinfo  (); ?> Axgle comments : A simple function that keeps you updated on the rapid development of PHP-if you are closely following the development of PHP ~~~~ 5. File_get_contents () (Note: PHP 4> = 4.3.0, PHP 5 ) Read the entire file into a string. . File_get_contents () Functions are the first choice to read the content of a file into a string. If the operating system supports it, the memory ing technology will be used to enhance the performance. For example : <? PHP  $ Data = File_get_contents ('Test.txt' );  Echo   $ Data  ; ?> 6. File_put_contents (Note: PHP 5 ) Write a string directly to the file. . For example : <? PHP  //  Address of an image $ URL = "Http://...test.com/plmm.jpg" ;  //  Read Binary "string"  $ Data = File_get_contents ( $ URL  );  //  Save to your computer  File_put_contents ("Beauty .jpg ", $ Data  ); ?> Axgle comments : If you find that an image of a beauty image website is named like 1.jpg, 2.jpg...OK, use a for loop to capture all the "beautiful women". Don't be so excited that your girlfriend will be jealous. ~~~ 7. Function_exists  If the function exists, true is returned. For example: : <? PHP  //  If the function does not exist, you can customize the function.  If (! Function_exists ('File _ put_contents' )){  Function   File_put_contents ( $ Filename , $ Data ){  $ Fp = Fopen ( $ Filename , "WB" );  Fwrite ( $ Fp , $ Data  );  Fclose ( $ Fp  );}} ?> 8. Get_defined_functions  Returns an array to obtain all defined PHP functions. For example : <PRE> <?PHP  $ Arr = Get_defined_functions  ();  Print_r ( $ Arr  ); ?> </PRE> Axgle comments : Now you know all the function names. If you want to know how to use a function, you can use http: //  Www.php.net/function_name can be found online, "manage all kinds of diseases, diagnose all kinds of problems and diagnose all kinds of problems, remove medicines to the disease ~~~~" 9. Get_declared_classes  Returns an array to obtain all defined PHP classes. For example : <PRE> <? PHP $ Arr = Get_declared_classes  ();  Print_r ( $ Arr  ); ?> </PRE> Axgle comments : You can see this function after Example 8 is run. Run this function in PhP4 to obtain only a few classes. However, if you use PhP5, you will see dozens of predefined PHP classes in this example! It can be seen that PhP5 is much more object-oriented. 10. Exit  Output the message and stop the current script. (Note: Like echo, this is not "Function", but a "statement" ). For example : <? PHP  Echo "Statement 1" ;  Exit ("The following statement 2 will not be output" );  Echo "Statement 2" ; ?> Axgle comments : It is useful to debug the program and find the wrong location. There are many useful PHP Functions And some very interesting PHP functions can be shared. I will introduce them later.