PHP Tips: 50 Practical tips for high-quality PHP code (Part One)

Source: Internet
Author: User
Tags closing tag learn php learn php programming
50 high-quality PHP code practical tips, I hope you like it.

1. Do not use relative paths
Often you will see:

Require_once ('.. /.. /lib/some_class.php ');

This approach has many drawbacks: it first finds the specified PHP include path, and then finds the current directory. Therefore, too many paths are checked. If the script is included in a script from another directory, its base directory becomes the directory where the other script resides.

Another problem is that when a timed task runs the script, its parent directory may not be the working directory. So the best option is to use absolute paths:

View Sourceprint? Define (' ROOT ', '/var/www/project/'); Require_once (ROOT. '.. /.. /lib/some_class.php '); Rest of the code

We define an absolute path, and the value is written dead. We can also improve it. Path/var/www/project can also change, so do we have to change it every time? No, we can use __file__ constants, such as:

Suppose your script is/var/www/project/index.php//then __file__ 'll always has that full path. Define (' ROOT ', PathInfo (__file__, pathinfo_dirname)); Require_once (ROOT. '.. /.. /lib/some_class.php '); Rest of the code

Now, no matter which directory you move to, such as a server that is moved to an extranet, the code will run correctly without changes.

2. Do not use require directly, include, Include_once, required_once
You can introduce multiple files in the script header, such as Class libraries, tool files, helper functions, and so on, such as:

Require_once (' lib/database.php '); Require_once (' lib/mail.php '); Require_once (' helpers/utitlity_functions.php ');

This usage is quite primitive. should be more flexible. You should write an assistant function that contains the file. For example:

function Load_class ($class _name) {//path to the class file $path = ROOT. '/lib/'. $class _name. '. php '); Require_once ($path); } load_class (' Database '); Load_class (' Mail ');

Is there anything different? The code is more readable. You can expand the function as needed, such as:

function Load_class ($class _name) {//path to the class file $path = ROOT. '/lib/'. $class _name. '. php '); if (file_exists ($path)) {require_once ($path);}}

You can do more: find multiple directories for the same file. It is easy to change the directory where the class files are placed, without having to modify them anywhere in the code one by one. You can use similar functions to load files, such as HTML content.

3. Keep Debug code for your app
In the development environment, we print the database query statements, dump the problematic variable values, and once the problem is resolved, we annotate or delete them. However, a better practice is to keep the debug code. In the development environment, you can:

Define (' Environment ', ' development '); if (! $db->query ($query) {if (Environment = = ' development ') {echo "$query failed";} else {echo "Database error. Please contact administrator "; } }

In the server, you can:

Define (' environment ', ' production '); if (! $db->query ($query) {if (Environment = = ' development ') {echo "$query failed";} else {echo "Database error. Please contact administrator "; } }

4. Execute commands using a function that can be cross-platform
System, exec, PassThru, shell_exec these 4 functions can be used to execute systems commands. Each behavior has a slight difference. The problem is that when in a shared host, some functions may be selectively disabled. Most novices tend to first check which function is available at a time, but then use it. A better solution is to marshal functions into a cross-platform function.

/** Method to execute a command in the terminal uses:1. System 2. PassThru 3. EXEC 4. Shell_exec */function terminal ($command) {//system if (function_exists (' system ')) {Ob_start (); System ($command, $retur N_var); $output = Ob_get_contents (); Ob_end_clean (); }//passthru else if (function_exists (' PassThru ')) {Ob_start (); PassThru ($command, $return _var); $output = Ob_get_conten TS (); Ob_end_clean (); }//exec else if (function_exists (' exec ')) {exec ($command, $output, $return _var); $output = implode ("\ n", $output);}/ /shell_exec Else if (function_exists (' shell_exec ')) {$output = Shell_exec ($command);} else {$output = ' command executio n not possible on the this system '; $return _var = 1; }return Array (' output ' = $output, ' status ' = $return _var); } terminal (' ls ');

The above function will run the shell command, as long as a system function is available, which preserves the consistency of the code.

5. Flexible writing functions

function Add_to_cart ($item _id, $qty)  {$_session[' cart ' [' item_id '] = $qty;} Add_to_cart (' IPHONE3 ', 2);

Use the function above to add a single item. And when you add a list of items, do you want to create another function? No, just a little attention to the different types of parameters, it will be more flexible. Such as:

function Add_to_cart ($item _id, $qty) {if (!is_array ($item _id)) {$_session[' cart '] [' item_id '] = $qty;} else {foreach ($i tem_id as $i _id = $qty) {$_session[' cart ' [' i_id '] = $qty;}} } add_to_cart (' IPHONE3 ', 2); Add_to_cart (Array (' IPHONE3 ' = + 2, ' IPAD ' = 5));

Now, the same function can handle different types of input parameters. You can refactor your multiple code to make it smarter by referencing the example above.

6. Intentionally ignoring the PHP close tag
I'd like to know why so many blog posts about PHP suggestions don't mention this.

<?php echo "Hello"; Now dont close this tag

This will save you a lot of time. Let's give an example:
A super_class.php file

Super extra character after the closing tagindex.php
Require_once (' super_class.php '); Echo an image or PDF, or set the cookie or session data

This way, you will get a Headers already send error. Why? Because "super extra character" has been output. Now you have to start debugging. This will take a lot of time to find the Super extra location. Therefore, develop the habit of omitting the closing character:

<?php class Super_class {function super_function () {//super Code}}//no closing tag

That would be better.

7. Collect all inputs in one place, one output to the browser
This is called output buffering, if you have output content in a different function:

function Print_header () {echo "Site Log and Login Links"} function Print_footer () {echo "site is made by Me";} Print _header (); for ($i = 0; $i < $i + +) {echo "I is: $i ';} Print_footer ();

Alternative, collect the output centrally in a place. You can store them in local variables of a function, or you can use Ob_start and Ob_end_clean. As follows:

function Print_header () {$o = "Site Log and Login links"; return $o;} function Print_footer () {$o = "Site is made by me"; return $o;} Echo Print_header (); for ($i = 0; $i < $i + +) {echo "I is: $i ';} Echo Print_footer ();

Why output buffering is required:
>> can change the output before sending it to the browser. such as the Str_replaces function or may be preg_replaces or add some monitoring/debugging HTML content.
>> output to the browser while doing PHP processing is very bad. You should have seen some of the site's sidebar or the middle of an error message. Do you know why it happened? Because processing and output are mixed.

8. Send the correct MIME type header information if the output is non-HTML content.
Output some XML.

$xml = "; $xml = "0";//send XML data echo $xml;

Work well. But some improvements are needed.

$xml = "; $xml = "0"; Send XML Data Header ("Content-type:text/xml"); Echo $xml;

Note the header line. The line tells the browser that the content of the XML type is being sent. So the browser can handle it correctly. Many JavaScript libraries also rely on header information.
Similar to JavaScript, CSS, jpg image, PNG image:

Javascriptheader ("Content-type:application/x-javascript"); echo "var a = 10"; Cssheader ("Content-type:text/css"); echo "#p ID {background: #000;}";

9. Set the correct character encoding for MySQL connection
Once encountered in the MySQL table set unicode/utf-8 encoding, Phpadmin can also be displayed correctly, but when you get the content and in the output of the page, there will be garbled. The problem here is the character encoding of the MySQL connection.

Attempt to connect to database $c = Mysqli_connect ($this->host, $this->username, $this->password); Check connection Validity if (! $c) {die ("Could does connect to the database host:". Mysqli_connect_error ()); }//set the character Set of the connectionif (!mysqli_set_charset ($c, ' UTF8 ')) {die (' Mysqli_set_charset () failed ');}

Once the database is connected, it is best to set the characterset of the connection. If your app supports multiple languages, this is a must.

10. Set the correct encoding options using htmlentities
Before php5.4, the character's default encoding is iso-8859-1 and cannot be output directly such as &Agrave; &acirc; and so on.

$value = Htmlentities ($this->value, ent_quotes, CHARSET);

After php5.4, the default encoding is UTF-8, which solves many problems. But if your app is multilingual, keep an eye out for coding issues.

11. Do not use gzip compression output in your app to allow Apache to process
Have you considered using Ob_gzhandler? Don't do that. There is no point. PHP only applies to writing apps. You should not worry about server and browser data transfer optimization issues.
Use Apache's Mod_gzip/mod_deflate module to compress content.

12. Using Json_encode to output dynamic JavaScript content
You can often use PHP to output dynamic JavaScript content:

$images = Array (' Myself.png ', ' friends.png ', ' colleagues.png '), $js _code = '; foreach ($images as $image) {$js _code. = "' $image ', ';} $js _code = ' var images = ['. $js _code. ']; '; Echo $js _code;//output is var images = [' Myself.png ', ' friends.png ', ' colleagues.png ',];  Smarter practice, using Json_encode:  $images = Array (' Myself.png ', ' friends.png ', ' colleagues.png '); $js _code = ' var images = ' . Json_encode ($images); echo $js _code;//output Is:var images = ["Myself.png", "Friends.png", "Colleagues.png"]


13. Check the directory Write permission before writing the file
Before writing or saving the file, make sure the directory is writable, and if it is not writable, output the error message. This will save you a lot of debugging time. Linux system, the need to handle permissions, directory permissions can cause a lot of problems, files may not be read and so on.
Make sure your app is smart enough to output some important information.

$contents = "all the content"; $file _path = "/var/www/project/content.txt"; File_put_contents ($file _path, $contents);

This is generally true. But there are some indirect problems. File_put_contents may fail for several reasons:
>> Parent Directory does not exist
>> directory exists, but not writable
>> file is written locked?
So it's better to do a clear check before writing a file.

$contents = "all the content"; $dir = '/var/www/project '; $file _path = $dir. "/content.txt"; if (is_writable ($dir)) {file_put_contents ($file _path, $contents);} else {die ("Directory $dir are not writable, or does n OT exist. Please check "); }

After doing so, you will get a clear message of where the file is written and why it failed.

14. Change the file permissions created by the app
In a Linux environment, permissions issues can be a waste of your time. Henceforth, whenever you create some files, be sure to use chmod to set the correct permissions. Otherwise, the file may be created first by "PHP" users, but you use other users to log on to work, the system will be denied access or open the file, you have to struggle to get root permissions, change the permissions of the file and so on.

Read and write for owner, read for everybody else chmod ("/somedir/somefile", 0644); Everything for owner, read and execute for others chmod ("/somedir/somefile", 0755);

15. Do not rely on the Submit button value to check the form submission behavior

if ($_post[' submit '] = = ' Save ') {//save the things}

Most of the above are correct, except that the application is multilingual. ' Save ' may represent other meanings. How do you tell them apart? Therefore, do not rely on the value of the Submit button.

if ($_server[' request_method ') = = ' POST ' and isset ($_post[' submit ')) {//save The things}

Now you're free from the value of the Submit button.

16. Define a static variable for a variable that always has the same value within a function

Delay for some time function delay () {$sync _delay = get_option (' Sync_delay '), echo "Delaying for $sync _delay seconds. ."; Sleep ($sync _delay); echo "Done";}

Replace with static variables:

Delay for some time function delay () {static $sync _delay = null, if ($sync _delay = = null) {$sync _delay = get_option (' sy Nc_delay '); } echo "Delaying for $sync _delay seconds ..."; Sleep ($sync _delay); echo "Done";}

17. Do not use the $_session variable directly
Some simple examples:

$_session[' username '] = $username; $username = $_session[' username ');

This can cause some problems. If multiple apps are running in the same domain name, the session variables may conflict. Two different applications may use the same session key. For example, a front-end portal that uses the same domain name as a backend management system. From now on, use the application-related key and a wrapper function:

Define (' app_id ', ' abc_corp_ecommerce '); function to get a session variable function session_get ($key) {$k = app_id. '.' . $key; if (Isset ($_session[$k])) {return $_session[$k];} return false; }//function set the session variable Function session_set ($key, $value) {$k = app_id. '.' . $key; $_session[$k] = $value; return true; }

18. Encapsulating tool functions in a class
If you define a number of tool functions in a file:

function Utility_a () {//this function does a utility thing like string processing}function utility_b () {//this function Does nother utility thing like database processing} function Utility_c () {//this function is ...}

The use of these functions is dispersed throughout the application. You might want to encapsulate them in a class:

Class Utility {public static function utility_a () {}public static function Utility_b () {}public static function Utility_c ( {}}//and call them as $a = utility::utility_a (); $b = Utility::utility_b ();

The obvious benefit is that if PHP has a function with the same name, you can avoid collisions.
Another view is that you can maintain multiple versions of the same class in the same application without causing a conflict. This is the basic benefit of encapsulation, without it.

Bunch of Silly tips
>> use echo instead of print
>> use Str_replace instead of preg_replace, unless you absolutely need
>> do not use the short tag
>> simple string with single quotation mark instead of double quotation mark
Remember to use exit after >>head redirect
>> do not call functions in loops
>>isset is faster than strlen.
Formatted code as in >>
>> do not delete loops or if-else parentheses
Don't write code like this:

if ($a = = true) $a _count++;

This is absolutely waste. Written:

if ($a = = true) {$a _count++;}

Do not attempt to omit some syntax to shorten the code. But to make your logic brief.
>> use a text editor that has a highlighted syntax display. Highlighting syntax can help you reduce errors.

20. Using Array_map to quickly process arrays
For example, you want to trim all the elements in the array. Novice May:

foreach ($arr as $c = + $v) {$arr [$c] = Trim ($v);}

But using Array_map is easier:

$arr = Array_map (' Trim ', $arr);

This applies the call trim for each element of the $arr array. Another similar function is Array_walk. Check out the documentation to learn more tips.

21. Validating Data Using PHP filter
You must have used regular expressions to verify email, IP address, and so on. Yes, everyone uses it that way. Now, we want to make a different attempt, called filter.
The filter extension of PHP provides a simple way to validate and check input.

22. Mandatory type checking

$amount = intval ($_get[' amount '); $rate = (int) $_get[' rate '];

It's a good habit.

23. If required, use profiler such as Xdebug
If you use PHP to develop large-scale applications, PHP takes a lot of computation, and speed is a very important indicator. Use profile to help optimize your code. You can use Xdebug and WebGrid.

24. Handle large arrays with care
For large arrays and strings, you must handle them with care. A common mistake is the occurrence of an array copy causing memory overflow, throwing fatal error of the Memories size information:

$db _records_in_array_format; This is a big array holding $ rows from a table each have a columns, every row is atleast 10 bytes * * = 2MB$CC = $db _records_in_array_format; 2MB moresome_function ($CC); Another 2MB?

This is often done when importing or exporting a CSV file. Do not assume that the above code will often cause the script to crash due to memory limitations. There is no problem with small variables, but it must be avoided when dealing with large arrays.
Ensure that it is passed by reference or stored in a class variable:

$a = Get_large_array (); Pass_to_function (& $a);

When you do this, pass the variable reference to the function instead of copying the array. View the document.

Class A {function First () {$this->a = Get_large_array (); $this->pass_to_function ();} function Pass_to_function () {//process $this->a}}

Unset them as quickly as possible, freeing up memory to relieve the burden of scripting.

25. Use a single database connection from start to finish
Make sure that your scripts use a single database connection from start to finish. Open the connection correctly at the beginning, use it until the end, and then close it. Do not open the connection in the function as follows:

function Add_to_cart () {$db = new Database (); $db->query ("INSERT into cart ..."); function Empty_cart () {$db = new Database (); $db->query ("DELETE from cart ...");

Using multiple connections is a bad thing, and they slow down the app because creating a connection takes time and memory. Specific cases use singleton mode, such as database connection.

This cheats is not very exciting, I believe it will be helpful for everyone to learn PHP programming.

Related articles:

PHP Tips: 50 Practical tips for high-quality PHP code (Part Two)

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